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The Official Report of Operation Crossroads 

Prepared under the Direction of the 
Commander of Joint Task Force One 


W. A. Shurcliff 

Historian of Joint Task Force One 


Wm. H. Wise & Co., Inc. 

New York 

Woods HoIg Ocsanographic institution 

Copyright, 1947 
Wm. H. Wise & Co., Inc. 

WISE books are trademarked 

Look for the WISE old bird ! 

Printed in the United States of America 

Pre fa 


Tests A and B of Operation Crossroads, perhaps 
the most elaborate scientific tests ever conducted, are 
described in this official report with no attempt to 
prove or disprove anything. Its sole purpose is to 
present facts on the origin, planning, and execution 
of the joint enterprise. 

The word joint needs emphasis. The Tests were 
neither Navy tests nor Army tests; this Report is 
neither a Navy report nor an Army report, and it has 
not been submitted to Army or Navy for approval. 
The Tests and the Report are the work of Joint Task 
Force One, an agency created by the Joint (Army and 
Navy) Chiefs of Staff and responsible only to them. 

The Report does not attempt to duplicate the capable 
reporting of the many experienced reporters who wit- 
nessed the Tests. Through the press the general charac- 
ter of the Operation is known to hundreds of millions 
of persons here and abroad. The world knows that the 
first explosion was an atomic bomb detonation in the 
air on July 1, 1946, sinking 5 ships, and that the second 
explosion was an atomic bomb detonation underwater 
on July 25, 1946, sinking 9 ships. 

But there is a wealth of information, much of it 
technical, which has not reached the public. Time was 
required to ferret out the significant facts; patience 
was required to piece them together ; ingenuity was re- 
quired to present the material without jeopardizing se- 


curity. For reasons of security a few results have been 
omitted. These few are mainly technical correlations, 
as between exact distance and damage, or exact dis- 
tance and pressure. Good public relations and the duty 
of the Services to the public demand that the fullest 
account possible be made available. 

The facts included should help the public form 
sound conclusions and participate in the planning of 
national and international policies. Bulk release of 
energy from the nucleus is new on the earth ; its por- 
tent is unlimited. But if it — and we — are to survive, 
it must be controlled. And adequate control cannot be 
achieved unless the people know the facts. 

The present official account was written by the same 
group which prepared the over-all top-secret report 
recently transmitted by Vice Admiral W. H. P. Blandy, 
Commander of Joint Task Force One, to the Joint 
Chiefs of Staff. 

To the many persons who helped in the prepara- 
tion of this Report, I extend my thanks. I am partic- 
ularly indebted to Mr. David Z. Beckler, Deputy His- 
torian, and Mrs. Virginia Shapley, Editor. 

W. A. Shurcliff, 
Historian, Joint Task Force One 

February 7, 1947 




List of Plates vii 

Foreword by Vice Admiral W. H. P. Blandy, U.S.N ix 

Chapter 1. Why Operation Crossroads! 1 

2. Early Problems 16 

3. Plans and Planners 27 

4. Technical Offensive 46 

5. Scientific Offensive 57 

6. Bikini Overture 89 

7. Test A. : Explosion in Air 104 

8. Test B. : Underwater Explosion 145 

Appendix 1. Organization Charts 173 

2. List of Principal Participating Officials 176 

3. Joint Crossroads Committee 181 

4. The Evaluation Board 182 

5. The President 's Evaluation Commission 183 

6. United Nations Observers 184 

7. Congressional Observers 185 

8. Support Vessels 186 

9. Target Vessels, Test A 190 

10. Preliminary Statement by the Evaluation 

Board on Test A 192 

11. Preliminary Statement by the Evaluation 

Board on Test B 195 

12. Preliminary Statement by the Evaluation 

Commission on Test A 200 

13. Preliminary Statement by the Evaluation 

Commission on Test B 202 

14. Test C (Cancelled) 205 

15. Chronology of Atomic Bomb Detonations 207 

Index 209 


All photographs are Joint Task Force One photographs ex- 
cept as follows : 

Fritz Goro, Life Magazine : Plate 4 lower, plate 5 upper, plate 8, 
plate 15 upper, plate 15 lower, plate 16, plate 24 lower, plate 32 

Acme: Plate 17. 



Frontispiece View of Test B 

Plate 1. Air Moek-up 

Press Conference 
Plate 2 Model of Bikini Lajsoon 

Fleet Assembled in Bikini Lagoon 
Plate 3 Photographic Towers 

Native Outrigger Canoes 
Plate 4 Carrier Plane Take-off 

Materiel Prepared for Exposure 
Plate 5 Naturalist at Work 

Sonobuoys Being Assembled 

Plate 6 Airplane Wing Spotted on Deck 

Plate 7 Telemetering Instruments 

Robot Boat 

Plate 8 Animals Prepared for Exposure 

Plate 9 Crushed Tin Can Gages 

Underwater Camera Equipment 

Plate 10 Testing Plane Engine for Radioactivity 

Plate 11 Camera Equipment in Airplane 

Plate 12 Foil Pressure Gage 

Pendulum-type Inclinometer 

Plate 13 Taking Water Sample 

Plate 14 Pyramidal Orientometer 

Cockpit of Drone Plane 

Plate 15 Turtle Pressure Gage 

Plate 16 Automatic Radioactivity Recorder 

Plate 17 Submerging the APOGON 

Plate 18 Test A— First Seconds 

Plate 19 Test A Panorama 

Plate 20 Test A— Fully Developed Mushroom 


Plate 21 Damage to the INDEPENDENCE 

Plate 22 Damage to the SKATE 

Plate 23 Damage to Airplane 

Damage to NEVADA 
Plate 24 Removing Radioactive Filter 

Testing Goat for Radioactivity 
Plate 25 Test B— Cinderella Ship 

Test B— Early Phase 
Plate 26 Test B— Bird's Eye View 

Test B— Early Phase 

Plate 27 Test B— Panorama 

Plate 28 Test B— The Enveloping Cloud 

Plate 29 Waves Breaking on Beach 

Effect of Waves on Bikini Island 
Plate 30 The SARATOGA Sinking 

Decontaminating the NEW YORK 
Plate 31 A Radioactive Fish 

Underwater Damage 
Plate 32 Chart of Bomb Burst 

Bomb Burst over New York 



Operation Crossroads was directed by the United 
States for purposes of national defense ; but its lesson 
has world-wide significance. The atomic bomb is defi- 
nitely not ^'just another weapon"; its destructive 
power dwarfs all previous weapons. Observers at 
Bikini saw the bomb sink great steel warships and, 
with its penetrating nuclear radiations, reach into 
ships' interiors to kill test animals. The explosions in 
air and underwater were very different spectacles, but 
their end results mean the same : death and destruction 
on an enormous scale. 

Only after the military implications of atomic en- 
ergy have been grasped by the people of the world will 
the way be clear for working out effective international 
control. Throughout its ten-month tenure. Joint Task 
Force One attempted to give the world an intimate 
knowledge of the purposes, execution, and consequences 
of the Tests. The present volume not only summarizes 
much of the information already given out, but pre- 
sents much material not previously disclosed. This 
volume, together with the recently published Pictorial 
Record, forms the final, and perhaps the most informa- 
tive release on the Operation. 

Vice Admiral W. H. P. Blandy, U.S.N. , 
Commander, Joint Task Force Ofie 




The gray-green dawn of July 25, 1946, en- 
veloped Bikini Atoll. The target fleet lay still, with 
'^Yoke" flags flying to signify all personnel had been 
evacuated. Like moving shadows the support vessels 
slowly filed out of the Lagoon. Last to leave was the 
flagship MT. McKINLEY. The Lagoon was deserted. 

Just over the eastern horizon puffs of cumulus 
clouds appeared, heralding perfect weather for the 
flnal atomic test at Bikini. As the time for the ex- 
plosion approached, men paced the decks, adjusted 
their binoculars, studied the deserted target fleet to 
fix in their minds the steel pattern soon to be shattered. 
Clearly visible was the doomed SARATOGA, floating 
majestically as she had throughout the war ; among the 
forest of masts could be seen the tall thin mast of 
LSM-60, the ship from which the bomb was suspended. 
Closer — fatally close — lay the mighty ARKANSAS. 

Men stared fascinated as the relentless count began. 
In a few seconds the awful explosion would come. Not 
few : Two ! One ! 



The results are history. Ships were crushed, and 
sank; two million tons of water and spray buried 
scores of ships. 

Even more deeply buried — lost in the drama of the 
moment — were the underlying problems, the guiding 
motive. Why plan an Operation Crossroads'? Why 
send 42,000 men, 242 ships, 156 airplanes, 4 television 
transmitters, 750 cameras, 5000 pressure gages, 25,000 
radiation recorders, 204 goats, 200 pigs, 5000 rats and 
why transport Numbers 4 and 5 of the atomic bomb 
family thousands of miles across land and sea for two 
brief moments of majestic destruction? 

The general answer is, of course, well known: It 
was imperative to find how to improve our Navy. 
As long as we have a Navy — and we will have one 
as long as the possibility of war remains — we want to 
have one of highest possible quality. We want ships 
which are tough, even when threatened by atomic 
bombs; we want to keep the ships afloat, propellers 
turning, guns firing; we want to protect the crews so 
that, if fighting is necessary, they can fight well today 
and return home unharmed tomorrow. 

Underlying this general requirement is a long list 
of specific questions. If" the list seems long, it is be- 
cause of the unequalled importance of the atomic bomb. 
This new bomb is no mere creator of dazzling light and 
peach-colored clouds; it shakes the very foundations 
of military strategy. The questions are many ; they are 
highly technical and eminently practical. They are not 


easily separated and cataloged. Years may be required 
to answer them, but answers must be found. 

Naval architects, for example, were asking: When 
naval ships are caught by atomic bombs bursting in air 
what are the ships' "weakest links ?" What parts fail ? 
Where should added strength be provided? Do we 
need heavier side plating, or merely stronger joints'? 
Which stands up best to the terrific stresses imposed 
by atomic bombs: riveted seams or welded seams? 
Does the ship's framework stand up? How about the 
decks, superstructures, and masts ? What happens in- 
side the ship, as to boilers and turbines? How about 
radio and radar? Are the guns damaged? Do fuel 
supplies escape and burst into flame? Is ammunition 

Important questions were asked about the ship's 
crew. Ship designers wondered how the crew would 
make out, whether men working below decks would 
escape unharmed, whether the blast wave or thermal 
radiation ("flash") or radioactivity would be most in- 
jurious. Most of all, they needed to know how to pro- 
tect the men. Medical men wanted information as to 
how injuries can be diagnosed fastest and what medical 
treatments are best. 

Naval tacticians were asking even more basic ques- 
tions. How far must a ship be from an atomic bomb 
to survive? To prevent more than one ship in a fleet 
from being sunk by one bomb, how far apart must the 
ships be spaced? And if a bomb is about to explode. 


what avoiding action should the ship take? Should 
topside men remain at stations, or should most of them 
rush below for protection ? How about harbors ? Are 
ships particularly vulnerable there *? How far apart 
should they be anchored to prevent one bomb from 
causing a large-scale ''Pearl Harbor"? 

Scientists and engineers were on the spot, too. They 
couldn't answer their own questions, and they were 
equalty unable to answer the majority of the questions 
asked by ship designers. Just what does an atomic 
detonation consist of? What fraction of the tremen- 
dous energy release goes into the pressure wave ? What 
fractions go into thermal radiation, gamma radiation 
and neutron radiation ? Major question marks on pres- 
sure were : How great is the pressure ? How fast does 
the pressure wave spread ? At any one spot, how long 
does the high pressure last and what is the impulse 
exerted? How strong is the suction which instantty 
follows the pressure? Questions as to the inevitable 
and deadly gamma radiation were : At what range is 
it fatal? Are men behind steel walls protected? How 
thick must the walls be? When does the radiation 
sickness begin? Can the men continue to man their 
battle stations even after they have received fatal doses 
of the invisible radiation? 

The effects of an underwater explosion were even 
more difficult to predict. Nobody knew how many mil- 
lions of tons of water would be thrown into the air, 
how many miles this water would be thrown, what the 


shape of the water cloud would be, how big the water 
''crater" would be, or at what ranges ships might be 
broken or capsized by the first giant solitary wave ex- 
pected to tower 100 ft. high from trough to crest. 

Complete unknowns were such matters as: What 
percentage of the lethal fission products from the 
underwater explosion would remain trapped in the 
water? How badly would these insidious products 
contaminate the target ships ? Would they seep inside 
the ships ? How long would their deadly effect linger ? 
What could be done to wash them awa}^? Would an 
entire harbor be seriously affected? 

If we could get answers to all these questions, then 
we could dare tackle the really big questions : Which is 
more serious, the explosion in air or the explosion 
underwater? What loss of military efficiency or gen- 
eral crippling of an actual fieet will result from an 
atomic bomb explosion? What new naval tactics are 
required? How should our shipbuilding program be 
modified? Are heavier ships now less valuable and 
lighter ships more valuable, or vice versa? Should we 
cut down our largest naval bases and make more of 
smaller size ? In short, what must be done for our Navy 
to be of maximum use in the next ten or twenty years 
of the Nucleonics Age ? 

Some persons urged calling off the tests. They 
pointed to the high cost, expected to be many millions 
of dollars. They condemned sacrificing seaworthy ships. 
They feared tidal waves and chain-reactions in sea 


water. They thought cracks might be made in the 
earth's crust, allowing sea water to rush into the white- 
hot interior and form catastrophic quantities of steam. 
They feared antagonizing other countries. Some per- 
sons suspected that the target ships would be spaced 
too far apart, so that the tests would be ineffectual. 

A few technical men said that the tests were un- 
necessary. They said that the atomic bomb had already 
been tested successfully at Alamogordo, New^ Mexico, 
at Hiroshima, and at Nagasaki. They had been told 
of the elaborate preparations made for the Alamogordo 
Test, of observers and scientific instruments that moni- 
tored the explosions over Japan. They knew of the 
careful inspections later made of the ruined Japanese 
cities and of the extensive studies of injuries suffered 
by the Japanese people. Some technical men said, in ef- 
fect : " If we assemble the data already available, make 
additional small-scale tests required, call in our best 
theoretical physicists, then merely by computation we 
can arrive at the results we need; we don't need any 
further atomic bomb tests." 

Technical men closest to the practical problems 
knew that no such makeshift would work. They knew 
that the Alamogordo test, although entirely successful 
as a demonstration, did not produce all the technical 
and scientific data needed. To be sure, the story ob- 
tained as to gamma radiation and neutron radiation 
was a good one. On the other hand the optical radia- 
tion data and pressure data were not as extensive as 


had been hoped; real gaps remained. And then, of 
course, no ships were involved. 

At Hiroshima and Nagasaki a few photographs and 
pressure measurements were made of the explosions, 
but almost nothing of value to physicists was learned. 
Physicists wanted actual values of the following: 
pressure, impulse, accelerations, shock-wave velocity, 
ranges and intensities of gamma radiation, ranges and 
intensities of neutron radiation, decrease of the 
gamma radiation during the first few hours. And med- 
ical men, arriving on the scene late, found it difficult 
to tell w^hat the early symptoms of the injured persons 
had been, and whether the injuries resulted primarily 
from flash burn, gamma radiation, or from secondary 
factors such as fires, and floods, lack of food, over-exer- 
tion, and lack of medical attention. 

Nor could model tests give the pl\ysicists their an- 
swers. At least four serious obstacles stood in the 
way. First, you can't make a model atomic bomb; you 
have to use TNT. To imitate even a small ''model" 
atomic bomb, you use an enormous pile of TNT, and 
the pile is so enormous that the whole test is spoiled, 
at least as far as close-in events are concerned. 

Second, model making is not the simple matter it 
may appear to hobby-shop artists; a model ship, for 
example, has to be not only the same shape as the 
actual ship, but the model's sides and decks must 
be almost perfectly to scale also. This means that the 
sides of a model transport ship, for example, must be 


paper-thin, and at the same time must have the same 
flexibility, elasticity, and plastic flow as the steel plates 
on the transport ship. Model beams must be of paper- 
thin material also. Even the rivets must be closely imi- 
tated. The upshot is, of course, that no such thing as a 
really comparable model exists; the model will show 
damage from the model explosive charge, but nobody 
will know what the damage means in terms of damage 
to real ships. Determining the vulnerability of compli- 
cated equipment such as ships' boilers by means of 
models would, of course, be almost impossible. 

Third, no one — not even the scientists in the 
Navy's Bureau of Ships or Bureau of Ordnance — 
knew how to fully interpret model studies of water 
waves, when the test to be imitated is the shallow- 
underwater explosion of 20,000 tons of TNT, or its 
modern equivalent, one atomic bomb. The crux of the 
difficulty is: the weaves don't ''scale" as other phe- 
nomena do. We can use a model fleet in a model lagoon, 
and we will be rewarded by obtaining a very fine model 
pressure wave. But the water waves will come out all 
wrong ; they are much too high. They must be corrected 
by some rather uncertain calculation. 

Fourth, we cannot imitate in a model test the sud- 
den release of fission products and the sudden emission 
of neutrons. 

Thus it appears to be a true paradox that to show 
what the smallest of bodies — the atom — can do in 
chain-reacting concert, we must use a testing ground 



many square miles in extent. In any smaller theatre, 
the atom's power cannot be displayed. 

But this can be said : Once the full scale tests have 
been held, then the model makers and model testers 
come into their own; only then can they prove which 
types of models correspond to the real thing and which 
do not; they can tell with assurance how their model 
water waves are to be corrected to represent waves pro- 
duced by the atomic bomb. 

Am^one could have thought up the idea of testing 
the atomic bomb against naval vessels. It is indeed 
routine to test each new weapon in all major applica- 
tions. The novelty of the proposed test of the atomic 
bomb against naval vessels would lie in the unprece- 
dented scale and world-wide importance of the tests. 
These were the unique elements which challenged the 
imagination of scientist, officer, and layman alike. 

The Los Alamos Laboratory, the group which has 
made all our atomic bombs, was probably the first 
to give serious consideration to "testing" the bomb 
against naval vessels. Even in 1944 Los Alamos scien- 
tists were looking into the possibilities of eventually 
atomic-bombing Japanese fleet concentrations. But 
Japan's navy was already doomed, and her ships were 
destined to avoid atomic destruction until July 1, 1946, 
at Bikini. 

Immediately following President Truman's epoch- 
introducing statement of August 6, 1945, announcing 
the atomic bombing of Hiroshima, naval men and lay- 


men began asking: ''What would such a bomb do to 
a battleship ? Or an entire fleet ? ' ' 

Senator Brien McMahon (D., Conn.), soon to be- 
come chairman of the Senate's Special Committee on 
Atomic Energy, was quick to ask that the new bomb 
be tested against naval vessels. In a speech of August 
25, 1945, he said, ' ' In order to test the destructive pow- 
ers of the atomic bomb against naval vessels, I would 
like to see these Japanese naval ships taken to sea 
and an atomic bomb dropped on them. The resulting 
explosion should prove to us just how effective the 
atomic bomb is when used against the giant naval ships. 
I can think of no better use for these Jap ships. ' ' 

Lieutenant General B. M. Giles, in Tokyo head- 
quarters, led off for the Army. On September 14, 
1945, he proposed that at least two atomic bombs be 
used in the destruction of the Japanese Fleet. The 
proposal was radioed that same day by Major General 
C. E. LeMay to Washington, D. C, w^here it was 
weighed by Lieutenant General C. A. Spaatz and also 
by General H. H. Arnold, Commanding General of the 
Army Air Forces. 

Only four days later. General Arnold put the mat- 
ter up to the Joint Chiefs of Staff, the country's top 
military group.* He asked that the routine destruction 
of surviving Japanese vessels — recommended on Aug- 

* The Joint Chiefs of Staff then consisted of: General H. H. 
Arnold, General G. C. Marshall, Admiral E. J. King, and Admiral 
W. D. Leahy. 


ust 28, 1945, by Admiral E. J. King, Commander-in- 
Chief of the U. S. Fleet and Chief of Naval Operations 
— be countermanded. He urged that a number of the 
Japanese vessels be made available to the Army Air 
Forces for use in tests involving atomic bombs and 
other weapons. 

The Navy's response, made by Admiral King on 
October 16, 1945, called for broadening the proposal 
by having the Joint Chiefs of Staff control the tests 
and by having all pertinent groups of Army and Navy 
participate. Admiral King recommended that one 
bomb be detonated in the air and another in the water, 
and he made the very significant suggestion that a few 
of our own modern naval vessels be included in the 
target array. 

To get detailed planning underway. General Ar- 
nold suggested on October 31, 1945, that the Joint 
Statf Planners, a permanent working committee of the 
Joint Chiefs of Staff, decide just what tests should be 
made and what groups should make them. The sug- 
gestion was accepted, and the Joint Staff Planners 
were asked on November 10, 1945, to proceed. 

Their first act (November 13, 1945) was to appoint 
an '^ad hoc subcommittee" to make a complete and de- 
tailed proposal. This Subcommittee, usually called the 
"LeMay Subcommittee," had the following member- 
ship — after three early changes : 

Major General C. E. LeMay (Steering Member) 

Brigadier General W. A. Borden 



Colonel C. H. Bonesteel 

Captain G. W. Anderson,' Jr. (Navy) 

Captain V. L. Pottle (Navy) 

Commodore (now Rear Admiral) W. S. Parsons 

The Snbcommittee met frequently during the next 
six weeks, and thrashed out in full all the tests' prin- 
cipal features. The most controversial issues were: 
Who should command the prospective Joint Task 
Force? Should the target vessels carry full loads of 
fuel and ammunition? 

Some of the Subcommittee members suggested 
that the Commander be chosen from Army officers 
having close familiarity with the Manhattan Project. 
Other members pointed out that the majority of the 
operation would involve principally the Navy: naval 
target vessels, naval supporting vessels, naval construc- 
tion of shore facilities, inspecting and appraising dam- 
age to naval vessels. The final decision was made by 
the Joint Chiefs of Staff who designated Vice Admiral 
W. H. P. Blandy. Admiral Blandy, an ordnance 
specialist though a naval line officer, had been Chief 
of the Bureau of Ordnance from 1941 to 1943. He had 
commanded large Army and Navy forces of multiple 
types in Pacific amphibious operations in 1944 and 
1945. Since November, 1945, he had been Deputy Chief 
of Naval Operations, Special Weapons, particularly 
charged with developing atomic energy devices and 
guided missiles. 



Debate was long and vigorous on the question of 
fuel and ammunition loads. Air Forces' representa- 
tives initially proposed having nearly every target ship 
carry full loads of fuel and ammunition, to show the 
maximum damage the atomic bomb could do, includ- 
ing secondary effects of fires and ammunition ex- 
plosions. Others opposed this proposal, pointing out 
that with the ships crowded abnormally close together, 
release and ignition of oil or gasoline from a single 
ship might set fire to all adjacent ships; the result- 
ing damage might give an entirely false picture of 
what would happen to ships in their normal spacing. 
Such fires might destroy much of the really significant 
damage and large numbers of important scientific in- 
struments too. (The satisfactory compromise reached 
is discussed in Chapter 7.) 

The work of the LeMay Subcommittee culmi- 
nated in a detailed plan submitted to the Joint Chiefs 
of Staff and accepted by them (with a few minor 
changes) on December 28, 1945. 

Vice Admiral Blandy w^as soon ready with a de- 
tailed administrative and technical plan of action. The 
Joint Chiefs of Staff gave preliminary approval to the 
plan almost at once, and then referred it to the White 
House. The President studied it, and added ' ^ Approved 
Jan. 10, 1946. (signed) Harry S. Truman." 

The next day, January 11, the Joint Chiefs of Staff 
designated Admiral Blandy Commander of Joint Task 
Force One, and directed him as follows: 


1. By direction of the President, you are 
designated commander of a task force under 
the Joint Chiefs of Staif for the purpose of 
conducting tests for the determination of the 
effects of atomic explosives against naval ves- 
sels in order to appraise the strategic implica- 
tions of atomic bombs including the results 
on naval design and tactics. You will organ- 
ize a joint staff with adequate representation 
of land, sea, and air forces. You will include 
civilian scientists in your organization. 

2. The general requirements of the test will be 
to determine the effects of atomic explosives 
against ships selected to give good representa- 
tion of construction of modern naval and mer- 
chant vessels suitably disposed to give a grada- 
tion of damage from maximum to minimum. 
It is desired to include in the tests both air 
detonation and underwater detonation if the 
latter is considered feasible. Tests should be 
so arranged as to take advantage of oppor- 
tunities to obtain the effects of atomic explo- 
sives against ground and air targets and to 
acquire scientific data of general value if this 
is practicable. 

3. You are authorized to deal directly with 
agencies of the War and Navy Department 
in all matters relating to the preparation for 
the conduct of these tests; including direct 
access to the Manhattan District. Usual serv- 
vice lines will be available for administrative 
and logistic support of forces assigned. . . . 



4. The Joint Chiefs of Staff will appoint as 
a separate agency, directlj^ responsible to 
them, an evaluation board (committee) for 
the express purpose of evaluating the results 
of the tests. This board will be available to you 
for advice during the preparation of the tests. 
Appropriate sections of your organization will 
collaborate with this board as necessary, and 
you will provide it with all necessary facilities 
it may require to fulfill its functions. 

5. You will prepare plans for the test in- 
cluding selection of a suitable site which will 
permit accomplishment of the test with ac- 
ceptable risk and minimum hazard. Your 
plans for the operation and final report will be 
submitted to the Joint Chiefs of Staff' for 
their approval. 

For the Joint Chiefs of Staff: 
/a/ A. J. McFarland 
Brigadier General, U. S. A. 

Authority was now complete for holding the most 
observed, most photographed, most talked-of scien- 
tific test ever conducted. 




Even before Joint Task Force One had been 
created, major problems were being tackled by the 
Army and Navy groups most interested. 

Choice of site was one of the biggest problems. Any 
number of relatively near-at-hand sites in the Atlantic, 
the Caribbean, and the nearer parts of the Pacific satis- 
fied many of the requirements, but none of these 
satisfied all of the requirements. What was needed was : 

A protected anchorage at least six miles in 
diameter. (It must contain not only the enor- 
mous target fleet but also the even larger sup- 
porting fleet.) 

A site which was uninhabited, or nearly so. 
(All inhabitants would have to be evacuated.) 

A location at least 300 miles distant from the 
nearest city. (Radioactive materials released 
in the air might menace persons scores of 
miles to leeward.) 

A location within 1000 miles of a B-29 base. 
(The airburst bomb was to be delivered by a 
B-29 bombing plane.) 



Freedom from severe cold and violent storms. 

Predictable winds directionally uniform at 
all altitudes from sea-level to 60,000 feet. 
( There must be no chance that the radioactive 
materials carried high into the air could be 
wafted back over the task force personnel by 
a fluke counter-wind.) 

Predictable water currents of great lateral 
and vertical dispersion; fast currents avoid- 
ing important fishing areas, steamer lanes, 
inhabited shores. (Radioactive materials re- 
leased in water must be dispersed reasonably 
rapidly, and without harm to persons or to the 
fishing industry. ) 

Control by the United States. 

Bikini won out. Its 162 inhabitants could be trans- 
ferred readily. The few^ coral heads obstructing the 
anchorage could be eliminated by dynamiting. 

Bikini's location is shown in Figures 1 and 2. It 
is one of the 34 atolls making up the Marshall Islands 
group. Discovered in 1526 by a Spanish sea captain, 
the islands were rediscovered by the English Captains 
Grilbert and Marshall in 1788. Germany annexed them 
in 1885, and they were mandated to the Japanese after 
World War I. In World War II they were occupied 
by the Japanese. 

Final choice of Bikini suffered one delay. Spokes- 
men for the fishing industry feared the explosions 






I O) 



I I <« I 

|. ^ to 











might kill millions of fish, even at great range. They 
feared also that whales or tmia fish might be abundant 
in the area, and might be killed, crippling various fish- 
ing activities in the Pacific. To evaluate any such dan- 
gers, advice was sought from the Fish and Wildlife 
Service of the U. S. Department of the Interior. The 
answer was definite : Bikini is so far from the migra- 
tory routes of whales at the time of year in question 
that no appreciable danger to whales exists; and the 
area is not critical for tuna fish or other fish of com- 
mercial importance. In particular, it is not a spawn- 
ing ground for west coast tuna. 

A real dilemma complicated the choice of dates for 
the atomic bomb tests. The reasons for holding the 
tests soon seemed very urgent ; yet the need for delay 
seemed equally real. On the urgent side, these facts 
were clear: (1) The scientific resources of the Navy 
and Army (and the Army's Los Alamos Laboratory in 
particular) were declining from their wartime peaks; 
every month that passed left fewer scientists avail- 
able to accomplish the highly technical mission lying 
ahead. (2) The supply of nontechnical service per- 
sonnel, too, was diminishing; before long it would be 
difficult or impossible to obtain officers, technicians, or 
crews for the enormous fleet. (3) Civilian scientists 
to be ''drafted" from universities were insistent on 
returning to their universities by early September ; if 
they were to be used, the tests would have to be held 
in the spring. (4) Army and Navy budgets were ex- 



pected to become continually smaller, and might easily 
be incapable of standing the expense. (5) Target ves- 
sels, particularly the obsolete vessels, could not be held 
available indefinitely. (6) Military and naval planners 
had to proceed with plans for future strategy and 
construction; the fundamental technical data were 
needed almost immediate^. 

But technical and nontechnical men alike saw the 
othe]' side. They saw that a suitable task force could 
not be assembled overnight, that much paperwork 
must be done before men could step forward to plan 
and execute the operation capably. They realized that 
readying the ships of the great target fleet would be 
an enormous job; months would be required even if 
many different shipyards cooperated in the work. They 
knew that a multitude of scientific instruments of en- 
tirely new types must be designed, built, tested, in- 
stalled. They knew that careful rehearsals of all tech- 
nical and operational phases would be required before 
anything like full value could be got from the Tests. 

After consulting all his deputies and advisers, Ad- 
miral Blandy named May 15, 1946, as date for the first 
Test, the explosion in air; the second Test, the ex- 
plosion beneath the surface of the lagoon, w^as to occur 
approximately six weeks later. The race against time 
was started. 

No one knows whether the race would have been 
won or lost. For on March 22 a delay was ordered ; the 
President directed that the Tests be postponed approxi- 



mately six weeks in order that Congressional observers 
could complete their legislative work and yet see the 
Tests. July 1, then, became the new target date.* 

What was the best altitude for Test A, the explosion 
in air? This question shuttled back and forth across 
conference tables for months. Scientists at Los Alamos 
and in Washington swapped arguments as to what alti- 
tude would produce sinkings at the greatest radius 
or what altitude would produce moderate damage at 
greatest radius. Clearly a low altitude w^ould better 
insure sinking the nearest ships; but a greater alti- 
tude would permit the blast wave to reach out farther 
and do at least moderate damage at greater radius. 
While these scientists were matching formulas and 
graphs in friendly tussle to arrive at the best choice 
of altitude, they were also re-studying the results of 
the Alamogordo, Hiroshima, and Nagasaki explosions. 

* One of the most unexpected results of the postponement was 
the opportunity it gave to the Task Force's Wave Motion Section 
to take the measure of the great tsunami ("tidal wave") which 
struck the Hawaiian Islands on April 1, 1946. When the postpone- 
ment was announced, the wave motion experts were en route to 
Bikini; accordingly, they were directed to go to Pearl Harbor to 
await further instructions. They had no warning there of the ap- 
proach of the tsunami, and did not get their 65 tons of wave meas- 
uring equipment into action. But they went to work quickly in- 
specting the inundated areas and piecing together all availahle 
evidence. A full report on the tsunami was issued later, and some 
of the information learned was put to use in perfecting plans for 
measuring homh- produced waves at Bikini. Mr. N. J. Hotter, head 
of the Section, was asked to assure the population hy radio that 
710 such, danger threatened in the forthcoming atoynic homh ex- 


A mock-up of the air op- 
eration planned for Test 
A is studied by Vice Ad- 
miral W. H. P. Blandy, 
Commander of JTF-1 , and 
Maj. General W. E. Kep- 
ner, Deputy Task Force 
Commander for Aviation 
(both standing) and 
Brig. General T. W. 
Power (kneeling). The 
Air Plan specified the po- 
sitions and courses of all 
Army and Navy planes, 
manned and unmanned. 

A Washington press conference question is answered by Rear Admiral 
W. S. Parsons, Deputy Task Force Commander for Technical Direction. 
Flanking Admiral Parsons are Rear Admiral T. A. Solberg, Director of 
Ship Material, and Dr. R. A. Sawyer, Technical Director. On the table 
is a model of Bikini Atoll. 

Pla+e I 

UPPER. Adm. Blandy (left) confers with the Joint Chiefs of Staff's 
Evaluation Board. Left to right are Lt. Gen. L. H. Brereton, Dr. K. T. 
Compton (Chairman), R. Adm. R. A. Ofstie, Vice Adm. J. H. Hoover, 
Maj. Gen. T. F. Farrell, and the late Gen. J. W. Stillv^ell. LOWER. 
Activity in Bikini Lagoon. 

Plate 2 

Steel towers were erected on several Islands fringing the lagoon to 
house automatic cameras and other instruments. Cameras are installed 
inside lead-walled vaults whose doors are arranged to close auto- 
matically after the filming has been accomplished, thus protecting the 
film from gamma radiation. 

Native outrigger sail- 
boats are of double- 
ender type; they can beat 
to windward without 
coming about. Thanks to 
their speed and stability, 
they are used even for 
hundred-mile trips across 
open ocean, from atoll to 
atoll. These boats, to- 
gether with their native 
owners, were evacuated 
aboard LST 1 108 to Ron- 
gerik, another of the 
Marshall islands. 

Plate 3 

The two supporting car- 
riers, SAIDOR and SHAN- 
GRI-LA, were used for 
launching Navy drone 
and drone mother planes, 
photographic planes, and 
helicopters; also for 
processing photographs. 
Navy drones were landed 
on Roi island. Only one 
accident occurred in the 
course of their operation. 
The carriers bore small 
forests of radio and radar 

On the only clear plat- 
forms available — ships' 
decks — nearly every kind 
of Army material was 
placed for exposure to 
the A-Day explosion. This 
exposure program, which 
was directed by Colonel 
J. D. Frederick of the 
Army Ground Group, in- 
cluded everything from 
machine guns, flame 
throwers, and radio sets 
to clothing, canned 
goods, medical supplies, 
and skiis. Crated equip- 
ment was secured to the 
deck by means of steel 
straps and bolts. The in- 
formation gained filled 
seven volumes. 

Plate 4 

Surrounded by collecting 
bags, bottles, knapsacks, 
and other paraphernalia 
cherished by naturalists, 
Dr. J. P. E. Morrison, As- 
sistant Curator of Mol- 
lusks at the U.S. National 
Museum, examines a sea- 
faring bird caught at Bi- 
kini. Careful censuses 
were made, both before 
and after the explosions, 
of principal types of ani- 
mal and plant life. 

Sonobuoys to be used in the two Tests are inspected before being 
moored in assigned positions in the target area. The column mounted 
above the buoyancy barrel carries a horizontal, eight-sided loop serv- 
ing as artificial electrical ground. Above this may be seen the small 

vertical antenna. 

Plate 5 

An experimental wing panel is mounted by the Army Ground Group 
on the deck of a target ship, to find the vulnerability of such panels 
to atomic bomb explosions. Visible along the deck are a tail fin, a 
stabilizer, and a range-finder. All items are clearly labeled for post- 
explosion identification. 

Plate 6 

This Navy-NDRC radio te- 
lemeter receiving equip- 
ment permits scientists 
miles away to follow the 
performance of un- 
manned planes flying 
through the explosion 
area. Eighteen amplifier 
channels decode and 
magnify the information 
radioed automatically 
from the drone planes. 
Permanent records are 
provided by the oscillo- 
graph, shown at the rear. 

Radio-controlled drone boats were used to traverse the target area 
after each test, take samples of lagoon water, and send back informa- 
tion as to extent of radioactivity encountered. Smoke signal equipment 
may be seen overhanging the stern. The boats were guided by trans- 
mitters aboard the BEGOR. 

Plate 7 

Goats, pigs, guinea pigs, and rats were exposed on many ships in 
Test A to show what effects would be produced by the shock wave, 
visible radiation, thermal radiation, and nuclear radiations. The ani- 
mals were given sufficient food and water to last ten days. Only pigs 
and rats were used in Test B. 

Plate 8 


The outcome: occasional major changes of mind, and 
new line-ups of those favoring greater or lesser alti- 

Meanwhile the operational men were talking feasi- 
hility. If it were much more convenient and accurate 
to set off the bomb atop a cheap tower, then that would 
be an argument for choosing an altitude you could 
reach with such a tower. Some thought was given to 
use of a tower, possibly on a headland if greater alti- 
tude was desired. Little thought was given to placing 
the bomb atop the mast of a battleship since this would 
probably mean sure and almost meaningless loss of the 
battleship, and in any case this would definitely limit 
the altitude to about 100 feet. The feasibility of sus- 
pending the bomb from a captive balloon was explored 
and rejected, since officers familiar with the erratic 
behavior of such balloons argued strongly against any 
such plan. 

Other forces also were at work to influence the 
choice of altitude. Some persons pointed out that a 
rather low altitude would make Test A rather similar 
to Test B in which the bomb was to be detonated at or 
just below the surface. Air Forces' spokesmen pointed 
out that dropping the bomb from an airplane would 
not only provide invaluable experience in precision 
atomic bombing but would also remove all restrictions 
on altitude of the explosion, permitting the bomb to 
be dropped from an optimum altitude. 



After all groups had given their views in full, the 
decision was made. It w^as based principally on the cri- 
terion of producing serious damage at greatest pos- 
sible range. While the exact altitude chosen is restricted 
information, it may be said that the altitude was sev- 
eral hundred feet. 

For Test B, the underwater explosion, the problem 
was debated even longer. Many pages would be re- 
quired to trace the arguments and counter-arguments 
for setting off the bomb a few feet above the surface, 
exactly at the surface, a few feet below the surface, or 
considerably below the surface. 

Some of the most interesting arguments were these : 
If the bomb were detonated just above the surface of 
the water, energy transfer to the water would be poor, 
most of the fission products would go upward in the 
mushroom, and, in general, the test would differ very 
little from Test A. Even if the bomb were detonated 
at the surface or very slightly beneath the surface, 
no reall}^ impressive underwater pressures would re- 
sult, and again the test would not be far different from 
Test A. In fact a detonation very slightly beneath the 
surface of the w^ater might be especially ineffective; 
neither the air pressure wave nor the water pressure 
wave would be maximized, and it is possible that a 
curtain of spray might be throA\ai up which would 
actually screen off a large part of the pressure wave 
in air and nearly all the thermal radiation, gamma 
radiation, and neutron radiation. 



The greater depth for Test B appealed to nearly 
everyone except the engineers who would have the job 
of placing the bomb at the specified depth and detonat- 
ing it there. Atomic bombs are new; none had ever 
been set off beneath the surface of the water. In at- 
tempting such an unprecedented act, it would be neces- 
sary to provide means of '' keeping in communication" 
with the bomb at all times, not only to fire it (or, in an 
emergency, to prevent its firing) but also to test it. 
Unique security problems were presented too, since 
for a short interval the bomb would be very close to 
thousands of persons not authorized to see it. 

So difficult was the decision as to the best depth of 
the bomb, that for a long time two alternative plans 
were carried forward side by side. Not until late in 
the winter was the final decision made : that the bomb 
was to be suspended at appreciable depth — beneath 
an ''expendable" ship. 

No one should think that these problems arose at 
expected times in well-crystallized form. They appeared 
unexpectedly; they had a habit of being almost inex- 
tricably tied up with other unanswered questions. 
Many of them arose even before the creation of Joint 
Task Force One on January 11, 1946, before clear 
lines of authority were established, before a firm direc- 
tive had been issued as to the principal purposes of 
the Tests. And the key persons concerned were usually 
scattered across the country. A question raised by a 
scientist at Los Alamos, New Mexico, might be sent by 



coded telegram to the Maiiliattaii Engineer District's 
office in the New War Department Building, in Wash- 
ington, D. C. ; here the question would be decoded — 
perhaps in somewhat puzzling form — and forwarded, 
say, to representatives of the Chief of Naval Opera- 
tions in the Navy Building. Here a definite reply 
might be delayed until a civilian adviser located at 
Princeton, N. J., had been consulted. By the time the 
Princeton expert had been brought to Washington, 
some of the Washington men might have been called to 
Roswell Field, New Mexico, where the B-29's were 
being readied. By the time the answer was ready, the 
spotlight of interest might have shifted ; a whole new 
set of questions might have taken the center of the 

Thanks to cooperative spirit, the telephone, the air- 
plane, and high priorities, the problems were solved. 
The way was cleared for detailed planning. 




Joint Task Force One began its ten-month 
lease on life on January 11, 1946. It had no time for 
leisurely growth. Administrators had to be appointed 
immediately. Tentative plans had to be formulated at 
once and approved within a few days. 

The growing infant had full backing. The Secre- 
taries of War and Navy immediately issued orders to 
give the Operation full support. Officers, enlisted men, 
scientists, and technicians, were made available as re- 
quired. Laboratory facilities were granted freely. 
Quarters were offered, as well as supply lines, funds, 
and equipment. Nearly every Service bureau, branch, 
and division shared in the effort. Thanks to highest 
priorities, the Task Force grew rapidly and smoothly. 

Meanwhile, Admiral Blandy was conjuring a name. 
''Crossroads" seemed good, but it was a word already 
in use in certain code work. The code people were con- 
sulted, and agreed to surrender the name. So, on Jan- 
uary 12, 1946, the Operation was christened "Opera- 
tion Crossroads." 

Admiral Blandy drafted the Task Force organiza- 
tion, and quickly assembled a central staff. He chose 



experienced officers from Army and Navy for the top 
command and staff positions ; the men were chosen for 
their ability to act promptly and skillfully, without ex- 
tensive instruction or deliberation. 

Rear Admiral W. S. Parsons was chosen to direct 
the technical and scientific work. He was given the 
title of Deputy Task Force Commander for Technical 
Direction. His responsibility extended to preparing 
the ships, instruments, and test animals, detonating the 
atomic bombs, and determining the results of the ex- 
plosions. Although he played a central role in the 
planning, even before the creation of the LeMay Sub- 
committee of which he became a member, his designa- 
tion as a Deputy Task Force Commander of Joint Task 
Force One was not actually formalized until February 
26, 1946. 

Atomic bombs were not new to Admiral Parsons. 
For over two years he had served at the Los Alamos 
Laboratory, where he was head of the Ordnance Di- 
vision. And he had flown in the Enola Gay on her his- 
toric flight to Hiroshima; he not only supervised the 
combat delivery of the Hiroshima bomb but personally 
assembled the bomb after the takeoff. His familiarity 
with the bombs and with Manhattan Project officials 
made it logical that he should be principal intermediary 
between Joint Task Force One and the head office of 
the Manhattan Project. Admiral Parsons' large and 
versatile technical organization is described in detail 
in a later chapter. 



To direct the extensive air activities of the Opera- 
tion, Major General W. E. Kepner of the Army Air 
Forces was brought in. His broad experience included 
service in the Marine Corps and Army Infantry in 
World War I, participation in the development of the 
use of lighter-than-air craft at Lakehurst, N. J., and 
several important Army Air Forces commands in 
World War II. As Deputy Task Force Commander 
for Aviation, General Kepner 's responsibility extended 
to Navy air operations as well as Army air operations. 
It included planning, organizing, and directing the 
operations. The many novel problems he faced are 
described in a later chapter. 

When it became clear that the Army Ground Forces 
also had a stake in the Tests, a Ground Forces' Ad- 
viser was designated: Major General A. C. McAuliffe. 
His duty was to advise the Task Force Commander on 
the planning, organizing, and execution of the Ground 
Forces' program, including exposure of a wide variety 
of Army equipment to the explosions. 

To handle the enormous quantity of problems aris- 
ing as to personnel, public relations, military security, 
ship movements, communications, and supply, a Joint 
Task Force operational and administrative staff was 
assembled under Commodore J. A. Snackenberg, Chief 
of Staff. Of his four principal assistants, two were 
drawn from Army and two from Navy. They were : 
Captain Robert Brodie, Jr. (Navy), Assistant Chief 
of Staff for Personnel ; Brigadier General (now 



Colonel) T. J. Betts, Assistant Chief of Staff for In- 
telligence; Captain C. H. Lyman (Navy), Assistant 
Chief of Staff for Operations ; and Brigadier General 
(now Colonel) D. H. Blakelock, Assistant Chief of 
Staff for Logistics. To handle the innumerable prob- 
lems which would inevitably arise in Washington, 
D. C, after the Task Force had left for Bikini, a special 
rear echelon group was created under the command of 
Rear Admiral F. J. Lowry. 

The relationship of positions of Commander, Dep- 
uty Task Force Commanders, Chief of Staff, and 
Assistant Chiefs of Staff is shown in Appendix I. 

Before discussing the technical phases of the Oper- 
ation, we shall describe the less glamorous but equally 
important problems encountered by Commodore 
Snackenberg and his assistants. 


Handling of personnel matters was a long and up- 
hill struggle. Personnel had to be recruited just when 
the majority of Service men were heading for the exit 
from military life. The trend had to be combated. Pleas 
were made to man}^^ officers and enlisted men on the 
point of returning to civilian life; special TAD's 
(orders for temporary additional duty) were drafted; 
promises were made that the men would be released 



immediately on completion of the Operation. In the 
Navy, which was to supply over 90 per cent of the 
personnel, the Bureau of Naval Personnel put its 
weight behind the drive. The Bureau of Ships, Bureau 
of Ordnance, Bureau of Aeronautics, and several other 
bureaus also dug deep for personnel. And the same 
cooperation was given by the Army. 

Mere numbers were not enough. It was specialists 
that were particularly needed. Especially hard to find 
were electricians, radio and radar men, oceanograph- 
ers, bomb disposal experts, veterinarians, experts on 
fish and blood. 

Particularly acute was the dearth of radiological 
safety men. During the re-entry stages after the ex- 
plosions, many lives might depend on the availability 
of men who could quickly and reliably detect danger- 
ous concentrations of radioactive materials on target 
ships, or in lagoon water. Such men, called monitors, 
were also needed to clear the way for the speedy re- 
moval of animals and apparatus from the exposed 
ships. Similarly, they were vital to the quick saving 
of target ships which might be on the verge of sinking. 
Several hundred recruits were selected and trained, 
but when the tests were postponed by the President, 
many resigned. More were recruited; they were given 
last-minute training before departing for Bikini and 
while at sea. Over 225 monitors were actually available 
in the crucial periods at Bikini; and although they 
were spread thin and worked long hours, they per- 



formed their tasks excellently. They have the honor of 
being charter members in a new branch of defense: 
radiological safety. 

The demand for photographers, too, far exceeded 
the supply. First, the Services were combed; then 
appeals were sent out to hundreds of ex-servicemen 
who had been trained in military photography during 
the war. Over one hundred responded. 

But corralling the men was only a part of the prob- 
lem. They had to be inoculated against diseases com- 
mon in the Paci^fic Theatre. They had to be assigned 
living and working space, fed, and transported. Rec- 
reation areas had to be provided on Bikini Atoll and 
elsewhere. Finally, problems as to their return, re- 
placement, and release had to be faced. 

Hiring of civilians was especially complicated also. 
Special contracts and payroll procedures had to be im- 
provised almost overnight. Some men were arbitrarily' 
placed on the Los Alamos Laboratory payroll; others 
were paid from funds in the .Office of the Secretary of 
the Navy. Nearly every Service department concerned 
with the handling of personnel groaned under the 
load of unprecedented problems demanding immediate 

Despite their unending problems. Captain Robert 
Brodie and his assistants worked along doggedly, and 
each time a ship headed out for Bikini, an effective 

* E.g. before the author could ohtain a civilian secretary, formal 
authority had to he obtained from the Joint Chiefs of Staff. 



crew was aboard; each time a group of experts was 
needed to solve some unexpected technical problem, 
the experts were there. 


Brigadier General T. J. Betts, Assistant Chief of 
Stai¥ for Intelligence, had a positive and negative func- 
tion. The negative job was maintaining military se- 
curity. Never before had a nation fanfared its most 
secret military weapon so closely before the eyes of 
the world. Never before had an atomic bomb been det- 
onated in front of the world press. Each man partici- 
pating was checked for character and loyalty.* Special 
pass cards were issued. Courier services were estab- 
lished for sending secret messages between Bikini and 
Washington, D. C. Photographs were developed only 
by authorized Joint Task Force One persons, and no 
photograph was released until it had been found to 
satisfy the security rules laid down by the Joint Chiefs 
of Staff. 

These security rules seemed to most persons to be 
reasonable. They permitted discussion of the objects 
of the Tests, the approximate locations of all target 
ships, the kinds and numbers of animals placed on the 
ships, the method of delivering the bombs, the types 

* Each woman, too. There were 37 women nurses at Bikini, 
although few of the 41,963 men there ever caught glimpses of more 
than a half dozen. 



of scientific information sought. And they permitted 
inspecting many of the damaged ships before and after 
the explosions, obtaining statistics on test animals 
killed, and rough values of the ranges at which ships 
were sunk or damaged. Approximate figures were 
given out as to the amount of radioactivity produced, 
and the degree to which crews would have suffered. 
Not to be released were facts as to bomb design, exact 
amount of energy released, exact position of the bomb 
at the instant of detonation, exact positions of the 
target vessels, correlations between damage and exact 
values of range, pressure, etc. More than enough in- 
formation was released to permit the world to see both 
the character and magnitude of the havoc a single 
atomic bomb can cause. 

The most important of General Betts' positive func- 
tions (see Appendix 2) was providing the public with 
a stream of accurate information. To General Betts 
and his Public Information Officer, Captain Fitzhugh 
Lee (Navy), it sometimes appeared that the public 
went out of its way to conjure distorted pictures of the 
planning and expected results. Some groups were 
prone to believe that the target ship array was sup- 
posed to resemble a typical fleet at anchor, or a fleet 
at sea. Some persons tried to build up the Operation 
into an ''Air Forces versus Navy" struggle, in which 
the goal was to see how many ships the Air Forces 
could sink with one bomb. Others pictured the Tests 



as more-or-less rigged shows to ''prove" that the Navy 
was not obsolete ; they hinted that the Navy feared most 
of all, and for that reason w^as avoiding, the deep- 
under-water explosion of an atomic bomb with its re- 
sulting possibility of extensive damage to ships. 

But perhaps the commonest distortion was as to 
the great calamities which were to threaten. Massive 
underwater landslides might be tripped off ; enormous 
tidal waves might sweep across the Pacific and devas- 
tate its shores; the very crust of the earth might be 
parted, with unimaginable consequences. The chain 
reaction in the bomb might spread to the water and the 
whole ocean might explode. Conjecture had no limita- 
tions except man's imagination. 

The majority of the misconceptions were gradually 
dislodged by the steady stream of facts issued to press 
and radio by Captain Lee and his assistants. Within 
the first few weeks after the creation of the Task 
Force, Captain Lee had prepared and issued over fort}^ 
bulletins, which covered nearly every phase of the 
Operation. Open news conferences were held too. Ad- 
miral Blandy and his staff sat across the table from 
dozens of the country's best correspondents and gave 
spot answers to their searching questions concerning 
the atomic tests. 

Again and again they explained that the Tests were 
not Navy tests but Joint tests, to be carried out at the 
request of the Joint Chiefs of Staif and with the 



authorization of the President and Congress.* They re- 
iterated that the Tests were not designed to prove or 
disprove anything, but merely to find the facts. They 
pointed to charts showing that the planned target 
arrays bore no resemblance to fleets in harbor or at sea, 
but were designed specifically to produce the optimum 
amount of technical data. Continual effort was made 
to deflate predictions of catastrophes. 

The last key to good public relations was provided 
when authorization was arranged for inviting press 
and radio to send representatives to Bikini. The Joint 
Chiefs of Staff recommended such a course on January 
10, 1946, and the Secretaries of War and Navy gave 
their endorsement on February 5 ; final approval came 
from the White House on March 14. Actual attend- 
ance was as follows : 

Test A Test B 
Representatives of U. S. press, radio, 
pictorial services, magazines, etc. 114 75 

Foreign press, one representative from 
each nation having membership in UN 
Atomic Energy Commission, plus two 
representatives from Great Britain 10 8 

* Even the task of keeping the public informed was made a 
joint activity. On March 8, 1946, the Joint Chiefs of Staff requested 
that individual Services cease expressing to the press their own 
fragmentary news and asked that they channel all news releases 
through the Task Force Commander's central puhlic relations 



Selecting the individuals was not easy. Far more 
persons applied than could be accommodated. It was 
essential to work out some impartial scheme of issuing 
the invitations. One view was : Invite individual per- 
sons directly, by name. The opposite view was: Pick 
the news agencies, and let them name their own repre- 
sentatives. This latter view finally prevailed. Another 
nice question facing Captain Lee was : Should he try 
to select news agencies most experienced in reporting 
scientific and military matters, or should the selection 
be broadened to include all kinds of news agencies, re- 
gardless of the bents of their experience "^ The latter 
course was chosen. Without doubt the result was that 
some representatives unskilled in technical and mili- 
tary reporting made the trip ; but a redeeming advan- 
tage was that accounts of the Tests appeared in nearly 
every type of newspaper and magazine, including even 
some of our most "feminine" magazines. 

Through a specially-created committee, press and 
radio agencies were enlisted in helping to make the 
final choice of the agencies to be invited. 

Captain Lee arranged for the majority of the press 
and radio men to be transported to Bikini in the 
APPALACHIAN, press headquarters ship, and for 
others to go by air. To avoid repeated problems of pro- 
tocol. Captain Lee arranged that preferences in living 
quarters and various nonprofessional privileges were 
to be granted according to age, the oldest correspon- 
dents being most favored. 



To help those correspondents who were starting off 
''cold," Captain Lee arranged, besides press confer- 
ences, various orienting schemes. Lectures were ar- 
ranged; motion picture films were prepared and 
shown; press packets of pamphlets on subjects rang- 
ing all the way from nuclear physics to the history 
of the Central Pacific were prepared and distributed. 
No effort was spared in making this the Z)es^-reported 
as well as being the mos^-reported technical experiment 
of all time. 

Li the Nucleonics Age it is still true that a single 
picture is worth a thousand words. Recognizing this, 
General Betts asked Captain R. S. Quackenbush 
(Navy) to plan an adequate nontechnical photograph}^ 
program, whereby the press men and the world at large 
could see vicariously all that security would permit. 
His enormous program is described in a later chapter, 
in connection with technical photography.* 

A sincere gesture of international goodwill was 
made by inviting foreign observers to see the explo- 
sions. The desire to invite foreign observers was ex- 
pressed by the Services and by large sections of the 
public even before the Task Force had been formally 
created. The Joint Chiefs of Staff were considering 
the matter as early as January 10, 1946. The State De- 

* A selection of over 225 of the photographs taken hy Captain 
Quackenhush's group is presented in "Operation Crossroads, Offi- 
cial Pictorial Record," published hy William H. Wise & Co., Inc., 
New York, New York. 



partment went on record in favor of the proposition, 
and, on March 14, President Truman approved the 

The Secretary of State accordingly asked our am- 
bassadors in the eleven foreign countries having mem- 
bership in the United Nations Atomic Energy Com- 
mission to invite those countries to choose their official 
witnesses. The countries and their representatives are 
listed in Appendix 6. 

The twenty-one global representatives selected as- 
sembled in Washington, D. C, and went b}^ special 
train to Oakland, California. There they boarded the 
PANAMINT, Bikini bound. 

Besides these foreign observers and a few partici- 
pating scientists from Great Britain, there were eight 
additional observers from Great Britain, four from 
Canada, and one from Australia. There were also a 
few press representatives invited from foreign coun- 

But Colonel H. B. Smith, Head of the Nonpartici- 
pating Observers Section, had many other observers 
to shepherd also. There were fourteen Congressional 
observers (see Appendix 7), eighty-seven Army and 
Navy observers, and twenty-two civilian scientist ob- 
servers. Congressional observers were considerably 
fewer than expected. The Joint Chiefs of Staff orig- 
inally set a quota of sixty but the invitations were not 
issued until late — after June 14, 1946, when Congress 
gave final approval to the Tests. 




Nearly every movement of the Task Force's 242 
ships and 156 airplanes was made, of course, by direc- 
tion of the Task Force Commander; but it was the 
responsibility of Captain C. H. Lyman (Nav,y), Assist- 
ant Chief of Staff for Operations, to plan and coordi- 
nate all such movements. Captain W. C. Winn (Navy) 
assisted in the directing of movement of vessels. He 
maintained records showing where each ship was, who 
was in command, what its mission and destination 
were. When additional ships were required, it w^as his 
job to obtain them; when certain ships were no longer 
needed, it was his job to see that they were reassigned. 

Captain Lyman was assisted by Colonel W. D. 
Graney in the planning and directing of air operations. 
He was assisted by Captain K. M. Gentry (Navy) in 
communication matters, including radio, television, 
and transmission of radio-photographs ; a schedule of 
348 individual radio frequencies was arranged, of 
which 163 were assigned to command and administra- 
tive groups, 107 to instrumentation groups, and 78 to 
press and radio groups. In the crucial matter of an- 
alyzing and predicting weather, Captain Lyman was 
assisted by Colonel B. J. Holzman and Captain A. A. 
Cumberledge (Navy), outstanding experts in aerology. 

Perhaps the two most important observer groups 
at Bikini were the Joint Chiefs of Staff's Evaluation 



Board and the President's Evaluation Commission. 
The Evaluation Board, whose members are listed in 
Appendix 4, was responsible directly to the Joint 
Chiefs of Staff and was to make careful technical study 
and comprehensive conclusions. The Evaluation Com- 
mission, whose members are listed in Appendix 5, 
reported directly to the President. It was not expected 
to make any highly technical studies. Preliminary re- 
ports by these bodies are included in this volume as 
Appendices 10, 11, 12, and 13. 


The supply, transportation, and maintenance of 
men and materials was the responsibility of Brigadier 
General (now Colonel) D. H. Blakelock, Assistant 
Chief of Staff for Logistics. The breadth of his work 
is indicated in Appendix 1. He was responsible for 
transporting the Task Force's 42,000 men and provid- 
ing them with military, technical, and personal equip- 
ment. (Approximately 1300 persons were flown from 
continental United States to Bikini and back ; approxi- 
mately 440,000 pounds of freight were flown from con- 
tinental United States to Pearl Harbor or to the Mar- 
shall Islands.) 

Keeping these four fast-working staff divisions 
working without any crossing of purposes was no easy 
matter. Frequent staff meetings proved helpful. Here, 
flanking an enormous table set in the center of a car- 



peted and air-conditioned room, Admiral Blandy and 
his deputies would confer for an hour or two. Problems 
weve presented and comments were invited from all 
present. In each instance Admiral Blandy or his Chief 
of Staff would make a summary as to the agreed-on- 
course and designate one man to take the necessary 

Between formal meetings there were innumerable 
informal meetings. Staff officials whether from Army 
or Navy were given adjacent offices so that they could 

* The author and other civilians present found these meetings 
impressive, both in their democratic method of procedure and 
the quick avaiJ^hility of facts. Almost never did an officer have to 
consult notes, or ask to get the information later. Usually, he had the 
answers at the tip of his tongue; and if he did not, he was flanked 
hy one or two junior officers instantly ready to cite case and num- 
ber. Again, since representatives of all Service groups were present, 
almost no question was outside the scope of the meeting. 

One mildly humorous case of failure to obtain straight-off a 
useful answer Jias stuck in the author's memory: An urgent dis- 
patch was sent off to the advance group at Bikini to find whether 
the coral heads obstructing navigation m the Lagoon were being 
removed successfully. But the actual form of the message was to 
the effect: "Are you havijig any difficulty in removing the coral 
heads?" The laconic reply came back: "Yes." Admiral Blandy 's 
comment drew broad grins from all the conferees: "We don't 
care whether he's having difficulty: of course he is. All of us 
have our difficulties. Send another dispatch and ask if he is over- 
coming his difficulties." 

Clairvoyance was effectively used by Admiral Blandy in solv- 
ing one problem — ■ a problem as to what to do with the unconsumed 
beer which might remain on Bikini Atoll during the evacuation 
for Test A. After other officers had proposed various solutionis, 
Admiral Blandy spoke up: "There really isn't any problem; if 
I kyiow anything about military men, there won't be any uncon- 
sumed beer." 



exchange memos and drafts promptly. Telephone direc- 
tories of Crossroads officials were issued every two 
weeks, to keep pace with expanding forces and con- 
stantly shifting quarters. Throughout the day, streams 
of new personnel would crowd in, new desks and file 
cabinets were wheeled in on creaking dollies; new- 
comers, unable to find empty chairs would perch on 
desk tops or sit on staircases In the midst of this 
apparent confusion, the ubiquitous telephone men 
worked with pliers and screwdrivers. 

A mammoth Operation Plan was prepared — a plan 
so vast and detailed as to suggest the Book of Fate 
itself. The Plan ' contained several thousand large, 
finely-printed pages* and served as a bible throughout 
the Operation. Heart of the Plan was a set of twenty- 
nine annexes, each a veritable encyclopedia on all plans 
relating to a given phase of the Operation. The titles 
of the Annexes are illuminating ; they are : 

Movement Plan 

Logistics Plan 

Communication and Electronics Plan 

Security Plan 

Safety Plan 

Air Plan 

Instrumentation Plan 

Bikini Evacuation Plan 

Re-entry Plan 

* It is a great tribute to the Government Printing Office that it 
could print and deliver this enormous plan in the space of a very 
few weeks. 



Plan of Operation on A-Day 

Plan of Operation on B-Day 

Photographic Plan 

Salvage Plan 

Army Ground Group Plan 

Public Information Plan 

Target Layout Test A 

Target Layout Test B 

Oceanographic Survey Plan 

Harbor Information 

Aerological Plan 

Boat Pool Plan 

Typhoon Plan 

Ship Preparation Plan 

Reboarding and Inspection Plan 

Air-Sea Rescue Plan 

Nonparticipating Observers Plan 

Rongerik Evacuation Plan 


Drone Boat Plan 

Several of the annexes, which themselves contained 
voluminous appendices and even appendices to appen- 
dices, were many hundreds of pages in length, and con- 
tained a wealth of charts, graphs, etc.* Civilians or 
others who may have expected the Task Force to be 
directed by a multitude of impromptu decisions made 
in the field were impressed with the completeness with 
which problems were anticipated and categorically 

* The Operation Plan was so complete that the writer, who 
studied it with some care, had throughout the Operation the im- 
pression of attending a good Technicolor motion picture of a re- 
cently-read hook. 



solved long in advance. Even the exposure times for 
the ten thousand most important photographs were 
worked out and clearly specified in the Operation Plan. 

One obvious advantage of the detailed, long-in- 
advance planning was that it left the Task Force Com- 
mander and his assistants relatively free to solve the 
few unpredictable problems that were bound to arise. 
Principal unpredictable matters were : weather, num- 
ber of damaged target vessels which would require 
beaching, extent of radioactivity to be found on target 
vessels. As we shall see later, weather forced postpone- 
ment of the "Queen Day" rehearsal of Test A, and all 
but forced postponement of the ''William Day" re- 
hearsal of Test B. It caused a half -hour postponement 
of Test A. The radioactivity remaining on target ves- 
sels after Test B was much more intense than most 
persons had anticipated; considerable delays in re- 
boarding, inspecting, and report- writing resulted, and 
the final disposal of the surviving vessels was greatly 

The planning was good. As later chapters show, 
the Task Force assembled without incident and the 
target vessels were moored in the positions decided on 
weeks in advance ; both Tests came off on the intended 
days; no one was injured by the explosions; and a 
great mass of technical information was gathered. A 
vast administrative machine had proved its power. 




Crossroads was above all a technical oper- 
ation. All planning was subservient to the primary 
mission: collecting technical information. 

Rear Admiral W. S. Parsons, as Deputy Task 
Force Commander for Technical Direction, led the 
technological offensive. As Assistant Chief of Naval 
Operations, Special Weapons, he played a large part 
in formulating Navy opinion as to how the Tests should 
be arranged ; and, as ranking Navy member of the joint 
LeMay Subcommittee, he helped draw up the formal 

His biggest job was analyzing the technical require- 
ments, breaking them into logical divisions, and setting 
up the necessary technical administration. With the 
assistance of Navy Captains Horacio Rivero and F. L. 
Ashworth, he found that the required technical activi- 
ties could be aranged under four distinct headings. To 
handle these activities, he set up two technical adminis- 
trative groups and two advisory positions. 

The largest of the two technical administrative 
groups was made responsible for the following: (1) 
preparing the target vessels, exposing them to the two 



explosions, determining the damage, and disposing of 
them; (2) the same for a wide variety of Army and 
Navy equipment, including airplanes; (3) exposing 
goats, pigs, rats, guinea pigs, mice, determining injury, 
studying the symptoms, and finding the best methods 
of diagnosis and treatment ; (4) decontaminating those 
ships made radioactive by the explosions. This group, 
which ultimately involved more than 10,000 men, was 
directed by Rear Admiral T. A. Solberg, w^ho assumed 
the title of Director of Ship Material. 

Perhaps the most publicized of the two groups was 
that containing the 500 scientists responsible for meas- 
uring pressure, light, nuclear radiations, w^ave height, 
etc. In charge of this group was Dr. R. A. Sawyer, 
Technical Director. 

Captain G. M. Lyon (Navy, Medical Corps) was 
named as Safety Adviser. His job was to prevent in- 
jury to personnel, either from hazards of normal type 
or from hazards (other than nuclear radiations) pe- 
culiar to this Operation. This included hazards to per- 
sons first reboarding the target vessels : 

Mechanical hazards, including danger from 
falling objects, slippery (oil-covered) sur- 
faces, weakened ladders, decks, gratings, 
and weakened tanks under pressure. 

Drowning in flooded compartments. 

Fires; escaping steam; hot surfaces. 

Electrical shocks due to damaged wiring and 
short circuits. 



Chemical hazards due to carbon monoxide, 
carbon dioxide, nitrous gases, alcohol and 
other vapors, ammonia, corrosive acids and 
alkalies, creosol cleaning solutions. 

Miscellaneous hazards, including contami- 
nated drinking water and food, escaping 
gases from chemical warfare munitions, 
secondary explosions of ammunition or 

Enumerating the hazards was simple, but to warn 
the thousands of men involved and instruct them in 
safe practice required much planning and thorough 
training.* Captain Lyon's designation as Safety Ad- 
viser was a logical one in view of his extensive war- 
time experience in chemical warfare technology and 
his close association with the Atomic Bomb Project. 

Colonel S. L. Warren (Army Medical Corps) was 
made Radiological Safety Adviser to Rear Admiral 
Parsons and also to Admiral Blandy. His job was the 

* Accidents were very few. No one was injured hy the explosion, 
and no one was seriously injured even hy indirect effects such as 
radioactivity . However, jive fatal accidents occurred. A Navy en- 
listed man, R. L. Mangum, Seaman First Class, drowned on March 
25, 1946. Captain J. E. Bishop (Army) was killed on June 24, 
1946, as a residt of being struck hy the propeller of a B-29 which 
was warming up on the airstrip at Kwajalein. A Navy enlisted 
man, J . D. Moran, Radioman First Class, was accidentally electro- 
cuted on July 4, 1946, on the albermarle. Lt. W. H. William 
(Navy) was killed on July 9, 1946, in an airplane crash on Roi. 
J. R. Reagan, Seaman First Class, died as a result of methyl alcohol 
poisoning on July 24, 1946. 



unusual one of advising as to dangers which would lurk 
in the invisible radioactive materials scattered on 
target vessels, in lagooji water and even in the atmos- 
phere itself. Col. Warren brought with him years of 
experience gained wliile he was Chief of the Medical 
Section of the Manhattan Engineer District. 

Preparing the target ships and support ships was 
an enormous job. The job was far greater than might 
be expected bv persons unfamiliar with the prob- 
lems. Admiral Solberg was called upon to execute 
quickly an enormous planning program and to or- 
ganize the extensive cooperation to be obtained from 
all major shipyards, from the Office of the Chief of 
Naval Operations, from the Commander-in-Chief of 
the Pacific Fleet and Pacific Ocean Areas, and from 
nearly every Naval Bureau. 

Perhaps the simplest part of the work was pre- 
paring the support vessels, listed in Appendix 8. There 
were 149 of these vessels, 36 of them being of consid- 
erable size, i.e., over 10,000 tons. 

Considerable remodeling was required on many of 
the ships. On the flagship MT. McKINLEY, forty more 
desks were installed and air conditioning was provided 
in two wardrooms and three staff cabins; television 
and radio teletype equipment was installed also. On 
the press ship APPALACHIAN a broadcasting studio 
was built and television and radio teletype facilities 
were installed; additional accommodations were pro- 
vided for officers and press representatives, and several 



wardrooms were air conditioned. Air conditioning 
equipment was installed in certain parts of the PANA- 

to be used principally by the Los Alamos group, were 
converted into great floating laboratories equipped 
with nearly every kind of machine tool and electrical 
instrument. Special laboratories were installed in the 
AVERY ISLAND. BURLESON, the animal ship, 
was remodeled into a great dirtless farm, a palatial 
hotel for animals ; biophysics, radiobiology, pathology, 
and hematology laboratories were installed also. 
LSM-60, the central or Zeropoint ship for the sec- 
ond test, was remodeled to permit lowering the bomb, 
in its watertight caisson, through a central bottomless 
well. Special photographic laboratories were built in 
SAID OR and other ships participating in the enor- 
mous photographic program. 

These remodelings were completed rapidly. The ma- 
jority of the work on support ships and target ships 
was done in the Naval Shipyards at Philadelphia, 
Bremerton, Mare Island, Hunters Point, Terminal Is- 
land, and Pearl Harbor. The work was based on de- 
tailed plans prepared by the Bureau of Ships. 

Many kinds of policy problems had to be solved 
before the shipyards could begin preparing the target 
ships — listed in Appendix 9. One fundamental ques- 
tion was : Should the ships be stripped of all equipment 



of value, or should tliey be left fully equipped ? Econ- 
omy-minded persons favored removing much of the 
valuable equipment such as guns, rangefinders, radar 
equipment ; but others pointed out that the equipment 
must be left on the ships if the tests were to yield the 
maximum information. The final decision was as fol- 
lows : Items of historical interest and all items actually 
needed for our active fleet, except for sample items, 
should be removed; other equipment should be left 

How much repair work should be done was another 
puzzle. For results to be fully significant, the target 
ships should resemble normal, fighting ships; that is, 
they should be in good shape. But a number of the 
ships were in fact not in good shape. A few had serious 
war wounds, patched only in makeshift manner; it 
was clear that the old wounds might be re-opened with 
misleading ease. Similar questions arose as to ships' 
machinery, ordnance equipment, etc., which suffered 
damage during the war. The decision was made that the 
ships and their equipment should, wherever feasible, 
be put in first class condition. The amount of repair 
work entailed was very great; but had this work not 
been done, it would have been almost impossible to tell 
after each explosion what damage was really caused by 
the explosion, and what damage should be attributed to 
prior circumstances. 

An unusual ''must" — not normally applicable to 
manned ships — was making the ships almost perfectly 



watertight. A fact not fully realized by the public is 
that the majority of warships — even warships which 
have never seen battle — leak slightly. Particularly in 
older ships, it is almost impossible to make all joints 
perfectly tight. The slight continual in-fiow of water is 
of no consequence ordinarily ; it is easily pumped out. 
But in this Operation, where the ships might have to 
remain for weeks without crews and without pumps 
operating, such leaks might be very serious. There was 
some danger that the captured Japanese ships 
NAGATO and SAKAWA might actually sink from 
this cause if they were left unattended for three or 
four weeks. 

Admiral Solberg's group gave much attention also 
to internal watertightness, a subject which may appear 
to laymen to be of little importance, but was actually of 
great importance. Ships expect to take punishment in 
battles, but place reliance on internal watertightnc ss to 
keep them afloat and mobile. Ships are, in fact, honey- 
combs of separate compartments.* 

In battle, hatches between compartments are closed 
securely. If a shell, bomb, or torpedo opens a hole be- 
neath the waterline, water pours in; but if the ship's 
watertight integrity is good, only the compartments 
adjacent to the hole are flooded. Other compartments 

* Exact numbers of watertight compartments in modern ships 
are kept secret. But it is no secret that for a modern U. S. battleship, 
for example, the number of such compartments is nearer 1000 than 



remain dry. Thus the ship can continue to cruise and 
to fight.* 

But it is very difficult to maintain internal water- 
tight integrity in older ships. In the first place, the 
older ships have far fewer compartments. Secondly, 
such ships have usually undergone considerable repair 
and remodeling, which means new holes cut through 
partitions for pipes, wiring, etc. It is almost impos- 
sible to seal these holes perfectly. Tests can be made, 
using compressed air, to see how tight any given com- 
partment is, and the leaks can be found; but the job 
is a very big one. 

Leaks between compartments would be especially 
serious in the target ships at Bikini. A typical ship 
might be left unmanned, with pumps shut off, for days 
or weeks. Water pouring into a single compartment 
might slowly spread throughout the ship and sink it. 
This, of course, would give a very false impression as 
to the effectiveness of the bomb ; even a skeleton crew 
might have prevented the flooding. 

Admiral Solberg's job, therefore, was to test water- 
tight integrity and to improve it so that the ships 
would have normal survival power, even when one or 

* During the war there were several occasions when a ship not 
only survived hut actually continued fighting after several holes 
had been torn in her hull plating below the ivaterline; there were 
even instances where ships were broken in halves, and yet one or 
both halves were kept afloat. The so-called "unsinkability" of the 
largest warships derives in fact more from effectiveness of com- 
partmentation than from mere toughness of exterior. 



a few holes were made in the hull by the great explo- 
sions. Thousands of compartments were air-tested; 
innumerable holes were filled, and the stuffing boxes 

Besides stripping the target ships of valuable ma- 
terial and putting them in good physical shape, the con- 
struction and installation of special mounts for scien- 
tific instruments was called for. Displacement and ac- 
celeration gages were to be mounted below decks, and 
a great variety of gages and automatic recorders were 
to be mounted topside. These mountings had to be 
very heavy in many cases to withstand the severe shock 
wave expected. Special stands or cages were installed 
for the test animals. Special fastenings were prepared 
for the wealth of army material to be exposed on the 
upper decks. Much special electronics equipment was 

Even before the target ships began heading out to 
sea, bound for Pearl Harbor and then Bikini, the enor- 
mous task of inspecting them was being planned. The 
two great explosions might create a wealth of dam- 
age ; but unless the damage were cataloged effectively, 
much value would be lost. 

Admiral Solberg's technical staff found that no ordi- 
nary inspection procedures would do. The procedures 
used during the war were studied* but were found not 

* During the war a very thorough systetn of inspections had 
heen worked out, for example, hy the Board of Inspection and 
Survey, Forces Afloat. 



to be adequate for the peculiar purposes of these Tests. 
A whole new set of instructions was therefore worked 
out and printed; it contained over 250 pages, and 
showed exactly how each part of the ship and each piece 
of equipment should be inspected. Equally important, 
it proposed standard forms for reporting the inspec- 
tion results. Without uniform reporting, it would be 
almost impossible to add up the information to get 
meaningful totals and comparisons. Two thousand 
copies of these instructions and five thousand inspec- 
tion notebooks were distributed. 

There was no formal parade of ships to Bikini, and 
little drama. Ships put out from east coast Navy 
yards as early as March 4, 1946. By mid-March the 
Panama Canal was making its contribution to the Op- 
eration. Many of the ships had left the west coast ship- 
yards by early March. Ships were drawn from remote 
Pacific bases also, including Manila, Shanghai, Guam, 
Okinawa, Saipan. The Japanese battleship NAGrATO 
came from Yokosuka, Japan, and the cruiser 
SAKAWA came from Otake, Japan. The German 
cruiser PRINZ EUGEN had come from Germany, via 
Boston, Philadelphia, and the Panama Canal. 

The great size of the Task Force became apparent 
at Pearl Harbor, where, in mid-May, over one hundred 
of the ships were assembled. But Pearl Harbor, fa- 
miliarly known as "Pearl" or "P.H.," was more than 
an assembly point; its huge shipyard had taken on 
the work of preparing a large number of the ships. 



Here also many of the target ships were loaded with 
ammunition and fuel. 

The migration of target ^hips towards Bikini was 
nearly completed by June 1. The focus of interest began 
to shift towards results. 




Science 's broad scope was clearly evidenced 
at Bikini. Boarding the ships and airplanes heading 
for Bikini were nuclear physicists, chemists, mathema- 
ticians, spectroscopists, roentgenologists, biophysicists, 
biologists, veterinarians, hematologists, piscatologists, 
oceanographers, geologists, seismologists, meteorolo- 
gists. Their work attracted particular attention because 
of its novelty. New kinds of phenomena were expected ; 
new kinds of instruments had to be built. No one could 
say whether the instruments would work properly, 
whether they would successfully cope with the extremes 
of pressure, radiation intensity, etc. The scientists were 
working at the frontier of experimental science ; some 
of them were working far beyond the known frontiers. 
They were filled with curiosity as to what information 
their instruments would capture from the uncontrolla- 
ble fury of the explosions which had never been wit- 
nessed by such a large body of scientists. 

Dr. R. A. Sawyer, Technical Director, arrived at 
Bikini on May 29, 1946. From his headquarters in the 
KENNETH WHITING, he and his assistants coordi- 



nated the final scientific preparations. Principal assist- 
ants were Dr. E. W. Thatcher, Captain F. L. Riddle 
(Navy), Commander E. S. Grilfillan, Jr., Commander 
A. W. McReynolds, Lieutenant Commander J. K. 
Debenham, and Ensign H. M. Archer. 

These men had little time for sunning on the upper 
deck, or watching the evening movies. Dressed in short- 
sleeved khaki shirts, abbreviated khaki trousers, -and 
sneakers, they worked in their small, hot, humid quar- 
ters from early morning until late at night. They had 
to study final plans, iron out the few minor inconsis- 
tencies, locate men to help out on lagging projects. They 
had to inspect installations, prepare progress reports, 
attend staff meetings on the MT. McKINLEY. 

The Venice-like transportation system was an ob- 
stacle. Each trip to inspect apparatus or attend a meet- 
ing meant traveling to another ship. Such trips usually 
took 10 or 20 minutes — if a launch was available. 
There were, of course, hundreds of small boats in the 
area, and all day they dotted the clear blue expanse of 
the Lagoon, their wakes crossing and interlacing. But 
the supply could not keep up with the demand. To make 
optimum use of these boats, scientists and others 
worked out boat pools, planned their work so that the 
minimum number of trips would be required. But 
throughout the Operation they were careful to culti- 
vate the friendship of the boat dispatchers. 

Dr. Sawyer had, of course, set up the necessary ad- 
ministrative organization long before he left Wash- 



ington, D. C. (See Appendix 1). Few final readjust- 
ments were required at Bikini. In creating this or- 
ganization, Dr. Sawyer made every attempt to make 
use of existing research groups ; for by using a group 
already staffed for a particular kind of research, re- 
sults could be obtained rapidly, with few personnel 
problems, little need for any extensive study, and 
almost no outside supervision. 

Although the administrative organization was de- 
signed to achieve maximum speed with minimum out- 
side supervision, it was not necessarily based on simple 
scientific lines. For this reason. Dr. Sawyer arranged 
coordinating groups to see that each scientific function 
was adequately taken care of. The functions covered 
included bomb operation, pressure and impulse, ocean- 
ography, electromagnetic propagation and electronics, 
radioactivity, optical radiation, nuclear radiation, 
technical photography, and remote measurements of 
various phenomena.* 

Dr. Sawyer's organization included more than 550 
scientists and engineers. The majority of them were 
civilians lent by the Services or by civilian agencies, 
foundations, and universities; many were Army and 
Navy officers. During their cooperative activities, 
civilian and Service personnel worked with little re- 

* Remote measurements included (1) measuring tide data at 
Midway, Wake, Kwajalein, and Eniwetok Islands, (2) recording 
shock at these islands, and (3) tracing radioactivity in the Central 



gard to protocol ; they sweated side by side to get the 
apparatus ready for recording the full measure of the 
great explosions of A-Day and B-Day. 


Pressure was to be king on A-Day, when the bomb 
was to explode several hundred feet in the air. It was 
expected that giant waves or intense gamma radiation 
might do the worst damage on B-Day, day of the under- 
water explosion ; but few doubted that pressure would 
wear the crown on A-Day. 

Air pressure may not sound fearsome. We are — 
literally — under pressure at all times. The air around 
us is compressed by the mere weight of overlying air. 
Every part of our bodies is subjected to a steady pres- 
sure of 14 or 15 pounds per square inch. Yet we sleep 
and breathe with ease. 

But although it is true that steady pressures of 
10 or 20 pounds per square inch go almost unnoticed, 
it is equally true that sudden increases in pressure 
(overpressure) can be remarkably effective. Fast, re- 
current pressure changes as slight as one billionth of a 
pound per square inch are easily detected by the ear ; 
many a building can be toppled by a sudden, transient, 
pressure increase of one pound per square inch. Tran- 
sient overpressure crtished thousands of buildings at 
Hiroshima ; it was to sink five ships on A-Day. 



Pressure experts cannot talk long about over- 
pressure without bringing in the Mach Stem, a scien- 
tific anomaly which makes pressure waves doubly de- 
structive to houses, ships, or other objects situated just 
above a large immovable surface. Near the end of the 
last century an Austrian scientist named Ernst Mach 
was studying electrical sparks — using apparatus plen- 
tifully coated with dust and soot. He noticed that 
whenever a spark was produced, dust was scoured 
away from a nearby, dust-covered surface. He noticed 
also that the scoured area was curiously limited in its 

The explanation is now well known. It is worth re- 
cording here since it had such a great influence on the 
planning and results of the A-Day explosion at Bikini. 
When an explosion occurs just above the surface 
of the ground (or say, just above the surface of a 
lagoon), the spherical pressure wave spreads in all 
directions. The part of the wave which strikes the 
ground is reflected. If the intensity of the direct and 
reflected waves is not too great, the waves go their sep- 
arate and easily-predicted ways. But if the pressure 
waves are very intense, then the whole situation 
changes : the waves affect one another curiously. Near 
the ground, in what has come to be called the Mach 
Stem region, the reflected wave finds itself close on the 
heels of the direct wave, in fact practically in the direct 
wave. Now it is a fact that when one intense wave 
travels more or less within another intense wave, it 



travels unusually fast. The result is that the reflected 
wave tends to catch up with — and even coalesce with 

— the direct wave. Actually the combined wave is no 
longer spherical, but nearly cylindrical or stem-like. 
All this happens, of course, only in the limited region 
where the two waves are initially fairly close together 

— i.e., near the ground. 

The scientific result is that near the ground the 
pressure is now far greater than could be produced by 
the direct or reflected waves singly. 

The tactical implications predicted for A-Day were 
ominous. The experts knew that a large fraction of the 
great armada of target vessels would find themselves 
in the Mach Stem region; what had been a scientific 
curiosity might mean destruction for many warships. 
Interest on this subject thus rose to an especially high 

Mere interest, of course, was not enough. Pressure 
gages were needed. Some of the simplest yet most 
effective gages were those devised by Dr. W. G. Penney, 
a British scientist. Back in 1945 when he was work- 
ing at Los Alamos, he made the daring guess that the 
humble tin can would prove to be one of the best "in- 
struments" for measuring the terrific pressures pro- 
duced by atomic bomb explosions. He soon showed his 
guess to be correct. He demonstrated that whenever a 
five-gallon gasoline can was partially crushed by a 
sudden pressure wave, the degree of crushing depended 
on the exact intensity of the pressure wave. For ex- 



ample, an overpressure of only a few pounds per square 
inch might reduce the can's vohime to 80 percent of 
the original volume ; but a more extreme overpressure 
might reduce the volume to 10 percent. Cans are cheap ; 
hundreds may be used, and the average effect can be 
measured with accuracy. (The decrease in the can's 
volume could be measured simply by filling the can 
with water, weighing it, and making a comparison 
with the weight of a filled tmcriished can). Many other 
instruments were equally ingenious. 

Dr. Penney and his assistants, collectively known 
as the Pressure Group (Cans and Drums), experi- 
mented with other gages of equally crude sort.* They 
were especially keen to hit upon gages good for meas- 
uring very high pressures. One type developed con- 
sisted of a sort of pan-pipes or harp, of small pipes 
of graded lengths. When the pressure wave strikes, 
the pipes are bent; long thin pipes bend most, and 
short fat pipes least. With the help of laboratory ex- 

* This Group included six subgroups, as follows: 
Air Blast Subgroup, headed by Dr. C. W. Lampson 
Underwater Subgroup, headed by Dr. A. B. Arons 
Low Frequency Subgroup, headed by Dr. J. V. Atanasoff 
Radiometry Subgroup, headed by Comdr. S. S. Ballard 
Pressure-Time Subgroup, headed by Dr. J. E. Henderson 
Service Subgroup, headed by CWO J. P. Orr. 
Captain L. W. McKeehan (Navy) served as Adviser. Personnel 
was drawn principally from the Navy's Bureau of Ordnance, the 
Naval Research Laboratory, and the David Taylor Model Basin; 
pressure experts were borrowed also from various U7iiversities, 
notably the University of Washington in Washington State. 



periments and some mathematics, Dr. Penney learned 
how to translate bends into pressure values.* 

Dr. Penney 's group was not the only one striving 
to extract knowledge from the pressure wave. The 
problem was attacked on a very broad front by the 
powerful Bureau of Ordnance Instrumentation Group. 
This Group, led by Captain A. E. Uehlinger (Navy) 
and under the technical direction of Dr. G. K. Hart- 
mann, surveyed all known types of pressure gages. 

But finding suitable gages was difficult ; there were 
many hard-to-meet requirements. Some of these re- 
quirements pervaded the other scientific fields, and 
were thus of especial importance. 

Most important was the requirement that the gages 
leave permanent records of their response; there 
would be no one on hand to watch them. Among the 
various automatic recording schemes available were: 
(1) ink-recorders, in which a small fountain pen writes 
its crude but significant message automatically on a 
sheet of paper mounted on a slowly-rotating disk or 
drum; (2) scratch-recorders, in which a needle 
scratches its message on a wax-coated disk or drum; 
(3) magnetic recorders, in which variations in pressure 
are converted into variations in degrees of magnet- 
ization of a short segment of a slowly-moving steel 
wire or tape; (4) optical recorders, in which pressure 

* /?i his official tour of inspection of Hiroshima and Nagasaki, 
Dr. Penney had found that the pressure waves there had left read- 
able records in the form of bent fence posts, sign posts, etc. 



variations cause a small beam of light to move across a 
slowly-traveling strip of photographic film, to be de- 
veloped and analyzed later; (5) telemeter-recording 
systems, in which pressure values are actually broad- 
cast by small, automatic, radio transmitters to wait- 
ing recorders located in some convenient places several 
miles away; (6) permanent-deformation gages, such 
as the Penney cans, which undergo permanent de- 
formations easy to interpret. 

A second requirement was that the gages be really 
rugged. Despite the need for using ingenious record- 
ing systems, the gages and their mounts must survive 
the terrific overpressure. It is pointless to use a pre- 
cision gage which is promptly flattened or blown over- 
board.* Hence delicacy was not a characteristic of 
the instrument cases taken to Bikini ; on the contrary, 
many of the designers enclosed their instruments' deli- 
cate worki^ in cases built of 2-inch-thick steel which 
could withstand the pressure. 

In the third place, the gages must resist corrosion. 
In the hot humid air, metal objects corroded unusually 
rapidly. Aluminum apparatus was, of course, very 
vulnerable to salt water. Thus corrosion-resistant 
metals were used ordinarily for exposed working parts, 
or waterproof coatings of paint or lacquer were ap- 

* In the Alamogordo test of June 16, 1945, a number of instru- 
meyxts failed to stand up to the U7iprece dented pressures. Some 
were crushed, others were torn loose and thrown considerable dis- 



In the fourth place, the gages must be able to bide 
their time. Even if the explosion were to be post- 
poned slightly, the instruments must be ready at the 
new H-Hour. Batteries must not run down; record- 
ers must be ready. In many cases the problem was 
solved by installing special starter-clocks; in other 
cases ''black box" remote-controlled starting devices 
were used. (These are discussed in Chapter 7.) In a 
few instances, the instruments were started by the flash 
of light emitted by the exploding bomb itself. 

A difficulty peculiar to the measurement of the 
pressure wave was designing instruments which would 
operate fast enough to catch the pressure wave at 
its instantaneous peak. For at any given point (say 
on a target vessel only a few hundred yards from the 
Zeropoint) the pressure would, of course, increase ex- 
tremely suddenly — so much so that the pressure ex- 
perts, when drawing sketches of the wave, usually pic- 
tured the wave as having what they called a ''square 
front." After its extremely rapid rise, the pressure 
would, of course, decrease again nearly as rapidly; 
then for a moment the pressure would actually fall to 
less than normal, in what is called the suction phase. 
Obviously a slow-acting gage would become confused 
by the many sudden changes in pressure, and would 
present only a sort of average value. Unfortunately, 
average values would be of little use ; every effort was 
made, therefore, to design fast-acting "mas!-let^.s" 



Fortunately, the pressure experts under Dr. Hart- 
mann had faced these problems back in the United 
States months before. Even during the autumn of 1945 
informal exploratory conferences were held among 
scientists and engineers from the Naval Ordnance 
Laboratory, the David Taylor Model Basin, and else- 
where. The difficulties were discussed, constructive 
suggestions were offered, criticized, revised, and slowly 
elaborated into sound designs. Whiteprints were 
rushed to the machine shops, finished instruments were 
tested, taken apart, adjusted and re-assembled. 

From many shops and laboratories, crates filled 
with instruments were started on their way by rail 
and air freight to the West Coast. The crates were 
almost always heavy, and stamped SECRET in large 
letters. Special shipping orders were prepared and 
guards provided. In all, over 5000 pressure gages made 
the journey, to snatch permanent meaning from tran- 
sient chaos. 

Even on the KENNETH WHITING, as she 
steamed westward at 16 knots, the specially-installed 
machine shop was busy with Ph.D's and technicians 
working with lathes, drill presses, and the ever-needed 

But now, as A-Day approached, emphasis shifted 
to installing the instruments. Let us look over the 
kinds of pressure gages which were installed. 

1. Can-Type Peak-Pressure Gage. This gage has 
been described on a previous page. Hundreds were 



made ready. In the expectation that some would be 
blown overboard, but might yet be rescued, many of 
them were tied to floats. An identifying number was 
marked on each can with a few crude strokes of a paint 
brush dripping red paint. 

2. Pipe-Type Peak-Pressure Gage. This gage also 
had been described on a previous page. The gages were 
bolted to the superstructures of the target vessels, par- 
ticularly the innermost vessels. 

3. Ball-Crusher Peak-Pressure Gage. This gage 
was designed to measure very high pressures. It con- 
sists of a strong hollow cylinder of metal, with a slid- 
able steel rod mounted in the hollow. When the pressure 
wave strikes, the rod is slid forcibly and strikes a 
small copper ball, flattening it. The greater the pres- 
sure, the harder the rod strikes and the flatter the ball 
becomes. The degree of flattening is later measured, 
and the pressure value calculated. Hmidreds of these 
gages were made ready. 

4. Ruptured Foil Peak-Pressure Gage. This gage 
was designed for intermediate pressures. It is ex- 
tremely simple. In one common form, it consists of a 
sheet of aluminum foil sandwiched between two heav,y 
metal plates. The plates have previously been drilled 
to provide a graduated series of holes of different size. 
When the pressure wave strikes, the tendency is for 
the exposed areas of the aluminum foil to bulge or 
even burst. Naturally, the larger exposed areas rup- 
ture most easily, and the small ones least easily. It is 



a simple matter, after an explosion has occurred, to 
inspect the foil, pick out the smallest area which burst, 
and thus compute the peak pressure. Hundreds of 
these gages were used. Typically, they were bolted to 
''Christmas trees,'' sturdy 9-ft.-high structures of 
heavy steel pipes. The Christmas trees were ordinarily 
welded to the upper decks of the target vessels. 

5. Deformed Plate Peak-Pressure Gage. This gage 
was used to measure fairly high pressure. It somewhat 
resembles the ruptured foil gage in operating prin- 
ciple, but employs a thicker foil or diaphragm, which 
ordinarily deforms without actually rupturing. A va- 
riety of designs were used to accommodate different 
pressure ranges. 

6. Indentation Peak-Pressure Gage. This gage also 
was capable of measuring very high pressures. Pres- 
sure is recorded in terms of indentation produced by 
a small steel ball forced against a sheet of lead. The 
greater the pressure, the deeper the indentation. 

In addition, various gages of more conventional 
type were used for measuring more moderate pres- 
sures. Some of these were of the familiar aneroid- 
barometer type. Others were of a liquid-trap type, in 
which the pressure wave depresses the liquid in a tube 
and causes some of the liquid to become trapped. 

Most elaborate of the pressure gages were those de- 
signed to trace the entire rise and fall of the pressure, 
i.e., the whole life history of the pressure wave as it 
swept past a given point. In some of these pressure- 



versus-time gages, pressure values are measured me- 
chanically, by small pistons moving against springs. 
In others, the principle of operation is electro-mechan- 
ical. The pressure wave moves a piston whose motion 
is opposed by a wire. The wire is thus strained to an 
extent depending on the pressure, and the wire's elec- 
trical resistance changes correspondingly. It is this 
electrical change which is actually recorded and later 
interpreted in terms of pressure. 

The five thousand pressure gages were placed with 
great care. The majority were placed topside on target 
vessels. Many were placed in especially unencumbered 
positions so that the pressure values recorded would 
not be invalidated by confusing reflections of the pres- 
sure wave. (Nearly every part of the ships' super- 
structures acted as a crude pressure-wave reflector, 
creating compound, hard-to-interpret, pressure situ- 
ations.) Gages capable of recording very high pres- 
sures were mounted on the ships nearest the Zeropoint ; 
gages of lower range were used on ships farther out. 
Gages designed to measure relatively low pressures 
were placed inside turrets, control rooms, and living 
quarters to show the pressures crews might experience. 
Even airplanes scheduled to be aloft near the target 
area were fitted with special gages. 

Nobody expected all the gages to deliver valuable 
data. A high ''disappointment rate" was anticipated. 
Some of the gages might fail to start ; others might be 
sunk with the ships they were on ; others might be dam- 


Some of the five-gallon 
cans which were exposed 
by Dr. W. G. Penny's 
Pressure Group at various 
distances from the A-Day 
explosion in air. Peak 
pressures produced at 
these distances were 
computed from the de- 
grees of crushing of the 
cans. Some of the cans 
were fastened to life- 
preservers so that they 
could be recovered if 
blown overboard. 


mm ~'*^p| 


""^A. "'^tm 




■ -m 



L. A 

■ VI 

" . . ».-i 









: K: 

Dr. V. E. Brock (right) and Ensign Richard Cron, Navy diver, examine 
a camera specially designed for use underwater, as in photographing 
damaged portions of sunken ships. This work was made difficult after 
Test B by the potential dangers from radioactivity in the water or in 
the ships themselves. 

Plate 9 

A "hot" engine on a B-29 is tested by means of a Geiger counter 
operated by Colonel R. L. Snider. The B-29's, which were part of Task 
Group 1.5, were based at Kwajalein. They were used for dropping 
the bomb used in Test A, photography, observation, and releasing 
special air-pressure gages. 

Plate 10 

Besides normal-speed and high-speed motion picture cameras, many 
mammoth still cameras were mounted in the photographic planes. 
Eight photographers are needed to operate the cameras in this C-54. 
The majority of the films were processed in an air-conditioned labora- 
tory constructed at Kwajalein. 

Motion picture cameras 
installed in a C-54 photo- 
graphic plane. The six 
Eastman high-speed cam- 
eras shown at the right 
are aimed up and down, 
right and left, by a single 
control handle. They op- 
erate one after another, 
automatically, so as to 
provide an uninterrupted 
record of the entire 
course of the explosion. 
The resulting films were 



UPPER. Dr. C. W. Lamp- 
son and Captain A. E. 
Uehlinger inspect a rup- 
tured-foil type gage for 
recording peak pressure 
in air. Ten aluminum foil 
disks of different size are 
visible. LOWER. Pendu- 
lum type inclinometer for 
automatically recording 
angles of roll and pitch 
of target ships. Records 
consist of scratches on the 
polished aluminum disks. 

Plate 12 

Members of Colonel S. L. Warren's Radioactivity Group sample the 
lagoon water by means of a Nansen bottle. Amounts of radioactivity 
in the water samples were determined with the aid of Geiger counters; 
the resulting data were entered on a "contour" chart showing the 
periphery of the "Geiger sour" area. 

Plate 13 

UPPER. Members of the BuOrd Instrumentation Group examine a deck- 
mounted pyramidal orientometer, a device for showing the direction 
from which the bomb's thermal radiation came. LOWER. Control 
panel of one of the B-17 Flying Fortress drones. 

Plate 14 

Final inspection and as- 
sembly of one of the 
thirty "turtles" specially 
designed by the BuOrd 
Instrumentation Group 
for recording pressure 
produced on the lagoon 
bottom by the huge 
waves generated by the 
B-Day underwater explo- 
sion. Pressure elements 
were of the Bourdon 
type, being actuated by 
water forced in by ex- 
cessive external pressure. 
Water entered through a 
fine capillary serving as 
a protective frequency 

Ready to plant a turtle 
on the bottom of the la- 
goon. The turtle cases 
were made of very heavy 
steel to prevent their del- 
icate contents from being 
flattened by the ex- 
tremely intense under- 
water shock wave. For 
ease of recovery the tur- 
tles were attached to tar- 
get vessels or special 
buoys by means of slack 
steel cables. However, 
several of the turtles 
placed near the center of 
the underwater explosion 
were never seen again. 

Plate 15 

In the Instrumentation Laboratory of the AG-76 AVERY ISLAND Mr. 
A. H. Waite, Jr., of the Radioactivity Measurement Section, checks the 
timing of an automatic pen-and-ink recorder. Such recorders were 
used on support ships to make permanent records of data gathered 
by automatic instruments on "hot" target ships. Several of the Geiger 
counters on the target ships v/ere employed in such telemeter system; 
readings were broadcast automatically to recorders on support ships 
stationed several miles from Bikini Atoll. The permanent records ob- 
tained were available for immediate use, or for more detailed analysis 
at a later time. Such data were of especially great importance in 
evaluating Test B, the underwater explosion. 

Plate 16 


aged by fires. Of course, the A-Day bomb might be 
(and indeed was) detonated at an miexpected position, 
which would mean that some gages would find them- 
selves nearer the detonation than had been expected 
while others would be unexpectedly far away; some 
gages, accordingly, would give readings so large as to 
be off-scale and others would read zero. 

Other complications were that the target vessels, de- 
spite their special moorings, were continually shifting 
with the tide and wind. Pressure gages intended for 
the exposed side of a target vessel might find them- 
selves actually on the shielded side. Then there was 
always the chance that the bomb itself would be ab- 
normally weak and would produce only abnormally- 
low pressures. 


To a physicist, impulse is no evanescent whim ; it is 
a prosaic but useful measure of cumulative push. It 
takes account of both the intensity of a push and 
the duration of the push, and is thus a compound con- 
cept. The intensity and the duration were both expected 
to be very great in the Bikini explosions. Engineers 
were undecided as to whether pressure, impulse, ve- 
locity, or acceleration data would be most useful in ex- 
plaining damage ; but all agreed that impulse was one 
of the important quantities to be studied if explosions 



and explosion-produced damage were to be fully under- 

Impulse can be computed directly from pressure- 
versus-time data.* It can also be measured by special 
gages which take account of intensity as well as dur- 
ation of pressure. A number of such gages were con- 
structed and placed at strategic locations on target ves- 
sels. No detailed description of these gages is neces- 
sary; many of them resemble some of the pressure 
gages described on the previous pages, but contain 
heavier, slower-moving pistons, better suited to taking 
a long view of things. 


Shock-wave is the name given to a pressure wave 
in its early, spectacular phase. To appreciate the spec- 
tacular phase, one must recall the relatively unspectac- 
ular behavior of most pressure waves. A typical pres- 
sure wave, such as the sound wave produced by banging 
a dishpan, leads a very dull life. It has no choice as to 
the velocity of spreading. It always spreads at exactly 
the same rate of roughly 1100 feet per second. This ap- 
plies to faint sounds and moderately loud sounds, to 
low-pitched sounds and high-pitched sounds. And such 

* It is well known that at moderate and great distances from 
an explosion, the overall impulse zV zero. That is, the initial push 
is exactly balanced by the pull of the ensuing suction phase. Close 
to the Zeropoint, however, the push always exceeds the pull, and 
the overall impulse has a net value greater than zero. 



a wave avoids suddenness: like an ocean swell, the 
pressure increases gradually and then decreases grad- 

But a shock wave has a personality of its own. In 
the first place, its intensity is so great that it cannot 
be content with spreading at the usual velocity — the 
velocity of the fastest jet planes; it demands higher 
velocity, equal to that of the fastest bullets. The more 
intense the shock wave, the higher its velocity. Sec- 
ondly, the pressure does not arrive at any given point 
gradually, but all at once. A building, tree, or ship may 
be enjoying an uneventful existence at one instant, but 
an instant later it may be reeling under the full im- 
pact by the pressure wave. There is absolutely no 
warning. The destructive effect is diabolically maxi- 

The most energetic explosions produce the most in- 
tense pressures and the most unusual Shockwaves. The 
experts at Bikini therefore went to great lengths to 
measure the A-Day shockwave. Spearheading the at- 
tempts to measure shockwave velocity was a group of 
high-speed cameras. Some of these, located atop special 
towers on Amen Island, were operated automatically 
and were capable of taking over 500 individual pictures 
each second. By use of short exposure times, and, of 
course, long focal length lenses. Captain R. S. Quacken- 

* This suddenness, or vertical front phenomenon, is due to tlie 
tendency of the hack part of the pressure wave to catch up with — 
and, so to speak, ride on the shoidders of — the front part. The 
result is of sledge-hammer severity. 



l)U8irs expert photographers hoped to produce the 
world's finest portraits of mammoth shock waves. 

Supplementing these cameras were other ingenious 
devices. Various kinds of shockwave detectors were 
placed at varying distances from the center of the 
target area. Some of the detectors were located on the 
target vessels; others floated on the water. Each de- 
tector was capable of sensing the passage of the shoe]-: 
w^ave and instantly dispatching a pre-arranged signal 
to monitoring apparatus located a few miles away. 
By such systems, shock-wave velocity could be deter- 
mined much as the British air-raid wardens were able 
to clock the rate of approach of a German airplane 
heading for London. In the Bikini tests, however, th(^ 
velocities would be many times greater, and the signal- 
ing had to be done without benefit of human hand. 


The most spectacular result of Test A was to be the 
terrific output of optical radiation, including visible, 
ultraviolet, and infrared light. The intensity was ex- 
pected to be greater than ever before produced on 
earth — except, of course, b}^ the previously detonated 
atomic bombs. 

The character of the light was not expected to ])e 
unusual. It has been known for many years that 
any very hot body tends to emit visible, ultraviolet, 
and infrared light. The atomic bomb, being extremely 



hot during the process of Hying apart, thus conforms 
with this rule. 

Measuring the total emission of light of all kinds 
was obviously desirable, since it would help to fix the 
total amount of energy released in the explosion. Also, 
it would help explain the flash burns to be produced on 
test animals and equipment. Measurements were ar- 
ranged by Commander S. S. Ballard and his colleagues 
from the Naval Research Laboratory. This group, 
called the Radiometry Subgroup of the Bureau of Ord- 
nance Instrumentation Group, had laid its plans long 
in advance. It had studied the optical radiation data 
obtained in the previous year's test at Alamogordo; it 
had estimated how greatly the absorption of Bikini at- 
mosphere would differ from that of the dry atmosphere 
of Alamogordo, and had then designed and build instru- 
ments ideal for the job at hand. Principal reliance 
was placed on bolometers and thermocouples, very 
small devices which detect without discrimination light 
rays of all kinds and directions. The received light pro- 
duces small electrical changes, which are amplified and 
ultimately cause small fountain pens to draw revealing 
curves on long sheets of graph paper. 

Of principal interest to the spectroscopists was the 
spectral distribution, or the relative amounts of light 
of short and long wavelengths.* These men wondered, 

* In these optical studies the Naval Research Laboratory spec- 
troscopists were assisted by spectroscopists from the Bureau of 
Ships, the Army Air Forces, and various private institutions. 



for example, how the intensity of ultraviolet light 
would compare with the intensity of visible light. Their 
wonderings led to the preparation of a number of dif- 
ferent instruments, each designed to answer a specific 
question. Several broad spectral bands, for example, 
were to be compared by means of photocells or electric 
eyes. Each of these electric eyes was deliberately made 
color-blind to all but a single color — by the use of 
''rose-tinted glasses," or glasses of any other color de- 
sired. Thus each photocell was made ready to report 
the results in its own spectral zone. For more precise 
discrimination between different parts of the spectrum, 
spectrographs were used. These employed small prisms 
and gratings to separate more cleanly the different 
wavelengths ; results were recorded on strips of photo- 
graphic film. 

High-speed techniques also were brought in. Com- 
mander Ballard knew that tremendous changes would 
occur in the emission of optical radiation during the 
first few instants after the detonation. The changes 
Avould occur hundreds of times too fast for the human 
eye to notice — even if the eye were not momentarily 
blinded. To catch these rapid changes, photocells were 
used. Their responses, free from any appreciable delay, 
were to be translated by means of cathode ray oscillo- 
graphs into the usual end-products dear to the heart of 
scientists : accurate and permanent charts. 



Size and rate of growth of the fireball came in for 
much attention. The creation of the atomic bomb had 
fascinated experts on thermodynamics who were ask- 
ing themselves : When the explosion first occurs, which 
gets oft' to the fastest start: the pressure wave? the 
optical radiation ? the nuclear radiation ? or actual ma- 
terials from the bomb ? Satisfactory answers were non- 
existent. Everyone agreed that at the instant of det- 
onation, the bomb, or at least what had been the bomb, 
is extremely hot. Its temperature is perhaps of the 
order of a million degrees Centigrade. And everyone 
agreed that every bit of matter which has that temper- 
ature cannot fail to emit enormous quantities of op- 
tical radiation. (It is well known, for example, that 
doubling tlie temperature of a hot body causes it to 
emit sixteen times as much energy, so that the rate of 
emission of energy from a body raised to a million de- 
grees must be staggering indeed.) But a tremendous 
complication at once sets in. The bulk of the energy is 
of very short wavelength, a wavelength which the at- 
mosphere refuses to transmit. Thus a curious kind of 
leapfrog must be taking place: the short- wavelength 
energy starts outw^ard, but before it has gone more than 
a few feet, it is absorbed by the surrounding air. The 
surrounding air, however, is so heated by having ab- 
sorbed this energy that it becomes highly luminous 
and itself radiates energy. This energy fares little 
better than the previous generation and is in turn ab- 
sorbed. So a sort of leapfrogging chain-reaction is set 



up, in \Yhich energy is l^eing constantly absorbed and 
re-radiated. The velocity of light is well known; but 
who knows the velocity of such a halting process ? The 
process cannot be imitated successfully in the labora- 
tory ; we have little to go on except estimates by ther- 
mod\^iamics experts — and close study of Test A at 

The rate of spreading of this optical radiation zone 
(rate of growth of the fireball) was to be measured 
principally by cameras. But no ordinary camera would 
do. Two special types, the O 'Brien and the Bowen, were 
obtained. Each of these had microsecond resolution; 
that is, each could distinguish what happened from one 
millionth of a second to the next millionth. Each was 
set up several miles from the target area center ; each 
was capable of charting the fireball 's development from 
birth to old age, a total span of only one or two sec- 

The lowly human eye was used also. In order to 
escape temporarj^ blindness, it had to be protected by 
dark goggles* or by the ingenious device called an 
Icaroscope. It was realized in advance that goggles 
could not be a perfect solution. Goggles satisfactory 
for the instant of greatest brightness would, of course, 
be too dark for the ensuing less-bright intervals. It 

* Most of the 6000 users of the special goggles found them too 
dark. This was due partly to the abnormally great extent to which 
light was absorbed in traveling for mayiy miles just above the 
surface of the water; also it ivas due partly to the desire of the 
safety advisers to make doubly sure that no one would suffer any 



would be necessary to throw aside the goggles durmg 
this important transition stage. 

A more versatile aid to the ''obsolete" human eye 
was the Icaroscope. This device, invented during the 
war by Prof. Brian O'Brien of the University of 
Rochester, represents the first use of the optical analog 
of the automatic volume control commonly used in 
radio sets. In the Icaroscope, excess brilliance is elimi- 
nated by means of an ingenious use of phosphorescence. 
Phosphorescent images, not direct images, are viewed. 
And whereas objects of intermediate brightness appear 
little changed, over-brilliant objects are subdued to a 
comfortable brightness. During the war the Icaro- 
scope permitted effortless visual detection of airplanes 
approaching directly ''out of the sun." At Bikini, 
over fifty Icaroscopes were made ready for viewing the 
almost-unviewable fireball. A few of the Icaroscopes 
were scanned by motion-picture cameras instead of 


Nuclear radiations, almost unknown to the public 
prior to the obliteration of Hiroshima, are now well 
known. Thus, gamma rays are true rays or waves; 
they resemble X-rays, but can penetrate even a foot- 

eye injury. The goggles actually transmitted only about 0.003 per- 
cent of the light striking them; without doubt a transmission two 
to ten times greater would have been better under the particular 
conditions prevailing. 



thick steel wall. Beta rays are particles. Specificall.y 
they are light-weight negatively-charged particles 
called electrons; they can scarcely penetrate a sheet 
of cardboard. Alpha rays are heavier particles and 
carry positive charges; they too have little penetrat- 
ing power. Neutrons are uncharged particles; be- 
cause of their lack of charge they are slippery, hard 
to stop. They can penetrate several feet of steel. 

In preparing for A-Day, Colonel S. L. Warren and 
other experts of the Radioactivity Group focused their 
attention on a period of one minute. They knew that in 
the A-Day Test, where the bomb was to be detonated 
in the air, the great bulk of the materials producing 
nuclear radiations would be carried upward by the 
fireball and the mushroom. Only during the first 
minute would the nuclear radiations be of outstanding 

There was no mystery as to the source of the nuclear 
radiation. It was known that the fission products 
would be highly radioactive.! Fission product s, of 

* It was expected that on B-Day, when the homb was set off 
underwater, the materials emitting nuclear radiations would he 
trapped in the water and would present a prolonged menace. Prep- 
arations for this more complicated situation are discussed in a 
later chapter. 

t Fissionable materials themselves can, of course he injurious. 
The Smyth Report states that among materials which are radio- 
active or toxic are to he listed not only fission products but uranium 
and plutonium themselves; uranium, aside from its radioactive 
properties, is poisonous chemically, and plutonium is alpha-radio- 



course, is the blanket name given to the fragments 
formed when atoms of uranium or phitonium are 
split. The splitting, which occurs within a small frac- 
tion of a second after the atom captures a neutron, 
does not always give the same kinds of fragments. In 
fact, more than 100 kinds have been identified.* Among 
them are : nuclei of atoms of bromine, krypton, rubi- 
dium, strontium, ytterbium, columbium, molybdenum, 
antimony, telurium, iodine, xenon, cesium, barium, 
lanthanum. As the bomb detonates, hilUo7is of hilUons 
of such fragments are flung out. 

To radiologists, the importance of these fission 
products lies in their instability. The products are not 
well-adjusted at the time of their birth, but go through 
tumid tuous "nervous breakdowns"; their electrical 
charge is poorly matched to their weight. Readjust- 
ment usually takes the form of emitting gamma rays, 
electrons, or neutrons. 

The principal questions asked by radiologists were : 
How rapidly do these readjustments come? How soon 
are they finished? Which type of radiation predomi- 
nates ? Of course, for any one kind of fission product 
the answers may usually be obtainable in the labora- 
tory; but the fission products are such a motley mix- 
ture, such an ephemeral hodge-podge, that their cumu- 

*A recent tabulation, presented in the Jouryial of the American 
Chemical Society for Novemher 1946, lists 160 fission products 
(including isotopes). 



lative effects are very difficult to predict. Studies have 
been made, of course, of fission products produced in 
the piles operating at Oak Ridge and elsewhere. But 
those fission products are born of a different process ; 
they result from fission produced by slow neutrons. 
Only when an atomic bomb explodes can the fission 
products of a fast neutron chain reaction be studied. 

From the tactical point of view^ this question was 
important: How far out does the gamma radiation 
reach ? It was well know^i that gamma radiation is ab- 
sorbed, by air; but definite answers were lacking as 
to just how many hundreds of yards of air were needed 
to protect exposed personnel. For neutrons, too, in- 
formation on shielding by air was incomplete. With 
respect to both gamma and neutron radiations, more 
information was needed as to the protection afforded 
by steel walls. It was recognized that persons located 
below decks would be relatively protected, but the exact 
extent to which such protection really would save lives 
was not known. 

Colonel Warren's group brought to Bikini more 
than 20,000 devices for measuring nuclear radiations. 
The commonest device used for measuring gamma ra- 
diation consisted merely of a small piece of unexposed 
photographic film wrapped so as to exclude all light. 
This device, called a badge, does its job silently and 
simply. When gamma rays strike the badge, they pene- 
trate the wrapping and produce a slight change in the 
photographic emulsion. When the badge's message is 



to be read, the badge is placed in photographic develop- 
ing solution, and the emulsion becomes darkened. The 
degree of darkening indicates the total amount of 
gamma radiation which struck the badge. Such badges 
were among the simplest and most reliable of all gages 
used at Bikini. Thousands were used for each of the 
two explosions. They were placed at innumerable posi- 
tions topside on target vessels, below decks, and in the 
same compartments where test animals w^ere sta- 

Geiger counters were to be used to find the intensity 
of gamma radiation at any one moment. These count- 
ers are especially useful because they produce their 
answers at once — either by motion of a needle across 
a dial, or by producing a machine-gun noise in head- 
phones. The marvel of the Geiger counter is that it can 
detect a single pJioton, or unit of gamma radiation. 
Heart of the counter is a crude electron tube, contain- 
ing a central wire and a small quantity of gas; the 
wire is at critically high voltage, such that the slightest 
disturbance — even the slight disturbance produced by 
arrival of a single photon of gamma radiation — com- 
pletely upsets the electrostatic regime and causes a 
violent discharge of current. Equilibrium is restored 

* Much operational use was made of such badges. They were 
carried continuously by persons working in contaminated areas 
where unsuspectedly large dosages of gamma radiation might be 
acquired. By developing and analyzing the badges, reliable an- 
swers could be found as to whether or not over-exposure had oc- 
curred. Fortunately, the answers were always in the negative. 



almost instantly, and the counter is ready to detect the 
next photon. Detecting and even counting these dis- 
charges is simple enough. Many different varieties of 
Geiger counters were prepared. Some were easily car- 
ried in the hand, for making quick spot checks. Others 
were equipped to operate for long periods of time with- 
out attention, recording their experiences on gi'aph 
paper or even radioing their findhigs to men and re- 
cording instruments located a few miles away. A few 
were equipped to operate underwater. Some were 
mounted in drone boats, a few carried in planes. 

Preparations were made for measuring alpha, beta, 
and neutron radiations also. Various standard types of 
instruments were used; far fewer were required than 
for gamma radiation. 


Noah would have felt at home on the BURLESON. 
But he would have been surprised at the selection of 
animals which Captain R. H. Draeger (Navy Medical 
Corps) brought. There were 200 pigs, 60 guinea pigs, 
204 goats, 5000 rats, and 200 mice. 

There was nothing haphazard in this choice. The 
animals selected must be capable of keeping in good 
health despite weeks spent on shipboard. Tropical 
weather must not wilt them. They must be amenable to 
remaining for days in confined quarters and com- 
pletely unattended. More important they must be of 



types already carefully studied ; it would be necessary 
to translate their reactions into reactions of men. 

Pigs were particularly valuable since their skin and 
short hair are comparable to man's. Goats were useful 
because their weight is comparable to man's and the 
quantity of their body fluid is sufficient for extensive 
laboratory analysis. Rats, time-honored experimental 
animals of radiology, were a logical choice since so 
much is known about their response to radiation and 
the correlation of their responses with man's. 

Some of the goats taken along were selected for 
their psychoneurotic tendencies. Psychologists thought 
that the severe explosion phenomena might change 
these tendencies. 

The mice were chosen from special strains show^- 
ing especially great likelihood of developing cancer, 
or especially small likelihood. Here too it was hoped 
that some interesting change would be produced, either 
in these mice themselves or in their progeny. 

No dogs were included. During the early planning 
of the operation many letters were received from the 
public urging that dogs be excluded.* 

Surprising though it may seem, the main purpose 
of placing test animals on the target vessels was not 
to find what percentage of the ships' crews would be 
injured or killed. That information could be obtained 
without using test animals. It could be obtained by 

* Over 50 jjercent of the letters of protest received from the 
public condemned the use of animals. A smaller percentage ex- 



instruments and calculations. Pressure gages, for ex- 
ample, would provide accurate knowledge of pressures 
produced. And previous history, such as that of Lon- 
doners exposed to German bombing attacks, had al- 
ready shown clearly what pressures would do to men. 
It was well known that sudden pressures of one hun- 
dred pounds per square inch could kill a man outright. 
It was known that pressures of only five pounds per 
square inch could throw a man so vigorously, that if 
his head struck a hard surface, he might be killed. For 
gamma radiation the situation was similar. Gages 
woul(J show the intensity of the radiation, and pre- 
vious experience in laboratories would show how to 
evaluate the data in terms of injury to men. 

The real purposes of using test animals were these : 
(1) to show the types of symptoms produced by the 
explosions; (2) to provide experience in cataloging 
injuries and detecting the onset of slowly-developing 
injuries; (3) to provide experience in treating injur- 
ies; and (4) to reveal any new^ kinds of effects. The 
injuries of principal interest were, of course, those 
caused by nuclear radiations. Such injuries were found 
at Hiroshima and Nagasaki, but the significant facts 
had often been lost in the welter of confusing circum- 
stances such as fires, floods, starvation, exposure, lack 

pressed fear of a widespread calamity. One writer was very grieved 
that the A-Day program was to come on a Sunday, intended to be 
a day of quiet and prayer; he expressed great relief when he was 
informed that Sunday in U. S. A. was actually Monday at Bikini. 



of medical care. Little success had been encountered in 
trying to reconstruct the relationship between injury 
and cause of injury. It was to fill such gaps that test 
animals were taken to Bikini. However, the number 
taken was kept to a minimum. 

Captain Draeger and his Executive Officer, Captain 
Shields Warren (Navy Medical Corps) were well sup- 
ported in their work. Starting with an important plan- 
ning conference held in early January 1946, at the 
Naval Medical Research Institution at Bethesda, Md., 
full cooperation by many agencies was obtained. These 
principal Arnw and Nav,y medical research agencies 
helped: Arniy Chemical Warfare Service (including 
the Biological Warfare Division), Army Medical 
Corps, Navy Bureau of Medicine and Surgery, Naval 
Medical Research IiLstitute. Also cooperating were the 
National Institute of Health of the United States Pub- 
lic Health Service, the United States Department of 
Agriculture, the National Cancer Institute, the United 
States Geological Survey, and various universities and 
private research agencies. 

The BURLESON began taking aboard animals at 
the end of May 1946, in San Francisco. The special 
accommodations provided for the animals were found 
to be very satisfactory. The ship began its westward 
trip on June 1; she started long after the other ves- 
sels, and made a fast run. The object, of course, was to 
have the animals in the best possible condition at the 
time of the first Test. 



Two weeks before Test A, the BURLESON passed 
through Enyu Channel and joined the 140-odd support 
ships already anchored at the northeast corner of the 




The SUMNER and the BOWDITCH were 
among the first of the ships to reach Bikini. In late 
January 1946, the Chief of Naval Operations arranged 
for these ships to proceed to Bikini to make needed 
surveys and oceanographic studies. SUMNER did the 
bulk of the hydrographic surveying. Her work was es- 
pecially urgent because the only available hydrographic 
charts of Bikini were Japanese and were quite inade- 
quate. SUMNER and assisting ships made some use of 
acoustical bottom scanners, but principal reliance was 
placed on wire-drag methods. 

The survey was finished in April, and the data were 
flown to the Navy's Hydrographic Office in Washing- 
ton, D. C, where the new charts were printed. Figure 
3 is a simplified chart showing the form of the 26- 
island Atoll. The earlier names of the Atoll's 26 islands 
were difficult to spell and would have been almost im- 
possible to handle in dispatches. Accordingly a set of 
simple code names was adopted by the Task Force. 
The two groups of names are as follows : 

Earlier Name Code Name 

Airukiiji , Arji 

Airukiraru Airy 
























Re ere 


















Enar , 














BOWDITCH, which arrived at Bikini on Marcli 
10, 1946, gave valuable assistance to the SUMNER.f 
But BOWDITCH '8 main job was making ocean- 

* This was later changed to "Prayer" to avoid confusion with 

t The BOWDITCH was huilt in Copenhagen over 30 years 
ago. She still retains her promenade deck, square portholes, and 
broad staircases. She was easily recognized hy her trailing column 
of black smoke. 



ographic, biological, and geological .surveys of the 
atoll. Aboard her were wave motion experts, icthvolo- 
gists, botanists, zoologists, and geologists drawn from 
the Woods Hole Oceanographic Institution, the Uni- 
versity of California's Scripps Institution of Ocean- 
ography, the Smithsonian Institution, the University of 
Michigan, the U. S. Geological Survey, the U. S. De- 
partment of the Interior's Fish and Wildlife Service, 
and the Army and Navy. These men, led by Lieutenant 
Commander C. A. Barnes of the U. S. Coast Guard, 
were the first scientists to reach Bikini, and they were 
among the last to leave. Their most urgent job was 
studying the lagoon currents to find out what might 
happen after the B-Day explosion, which would cer- 
tainly disperse enormous quantities of radioactive ma- 
terials in the water. Prompt re-entry into the target 
area would depend largely on accurate knowledge of 
these previously-uncharted currents. 

The BOWDITCH'S scientists also took censuses of 
populations of fishes, corals, and other animals, to per- 
mit later evaluation of the effects of the bombs on ani- 
mal life of the atoll. Fish were caught with hook, net, 
and seine. In some instances, the fish were poisoned 
with rotenone and picked up dead. To increase the sig- 
nificance of the censuses, similar censuses were taken at 
unaffected ''control" atolls, Rongerik and Rongelap, 
125 miles upwind, and also at Eniwetok, 200 miles 
downwind. Botanists made systematic surveys of plant 
life, and geologists gave the atoll the most thorough 



going-over ever accorded one of these billion ton piles 
of skeletal remains. 

The order to evacuate the natives came from the 
Navy Military Government Officer in February, when 
choice of Bikini as the test site became final. The 
Bikinians, convinced that the Tests would be a contri- 
bution to world peace, indicated their willingness to 
evacuate.* Their decision was reached at a meeting of 
the Atoll Council. Nine of the eleven alaps (family 
heads) named Rongerik Atoll, 128 miles to the East, as 
their first choice for resettlement. Lajrwe, Paramount 
Chief of Rongerik, concurred in this proposal. The trip 
was made on March 7, 1946, on LST 1108. Although 
much effort was spent to establish the Bikinians com- 
fortably on Rongerik, some dissatisfaction and nos- 
talgia have been apparent. Whether they will remain 
there is uncertain; radioactivity at Bikini renders 
their return there unsafe at present. 

Japanese mines had to be cleared from Bikini 
Lagoon before the support and target fleets arrived. 
Thirty-five mines had been located and removed dur- 

* Juda, Magistrate of Bikini Atoll, commonly called King of 
Bikini, witnessed one of the Tests, hut the other 161 inhabitants 
obtained only second-hand accounts. He was flown back to Bikini 
the day preceding B-Day, before final approval for such a visit 
had been obtained from the Joint Chiefs of Staff. He was received 
aboard the flagship MT. McKINLEY amid much embarrassment. 
The situation was saved by a quick interchange of radiograms with 
the office of the Joint Chiefs of Staff' in Washington, D. C. Word 
came back to Bikini that the Task Force Commander might "use 
his judgment" in the ^natter. 



ing September and October of 1945 by Task Unit 
96.38.1 under the Commander of the Marshall-Gilberts 
Area. Five more mines were removed during March 
of 1946 by Commander, Minecraft Pacific, Task Unit 

Coral heads were another menace to navigation 
inside the Lagoon. They consisted of great underwater 
obstructions rising nearly 200 feet above the lagoon 
floor. Many of them extended up to the level of the 
lagoon surface. Composed of corals and also deposits 
made by the calcerous algae, they were solid enough 
to damage any ships which might collide with them. 
Some were in positions to interfere with the mooring 
of target vessels or to impede the submerging of the 
target submarines. Accordingly, the tops of these coral 
heads were removed by dynamiting. Over 100 tons of 
dynamite were used. 

Much construction work was required on Bikini 
Atoll. Principal structures built were the following: 

. 12 75-ft. steel towers for mounting cameras 
and other technical equipment. (In view 
of high winds prevailing, these towers 
were constructed in horizontal position 
and then hoisted into vertical position.) 
5 25-ft. wood towers 
12 20 ft. X 20 ft. steel huts 
5 Seismograph huts 

5 '^ Dead-man" moorings for Test C 

6 Photography beacons, for aerial photog- 
raphy fixes 



■ 1 Club (20 ft. X 200 ft.) for officers and 
1 Club (16 ft. X 300 ft.) for enlisted men 
5 Concrete basketball courts 
10 Volley ball courts 

4 Softball diamonds 

1 Trap-shooting range 

1 Concrete athletic court (100 ft. x 100 ft.) 

26 Dressing huts 

1 Water distillation and distributing system 

1 Shore patrol and dispensary building 

3 Life-guard platforms 

1 Seaplane landing ramp 

2 Swim floats 

7 Pontoon causeways 

1 Air-coordination station 

3 Construction battalion shops 

1 Sonobuoy work shop 

10 Wave-height measurement piles 
14 Shallow-water moorings for evacuation 
barges and other small craft 

2 Radio beacons 

5 25-man camps 

1 Aerological station 

This construction was done by the 53rd Naval Con- 
struction Battalion. The first group of the Construc- 
tion Battalion to arrive at Bikini was a survey party 
which arrived on March 11. By March 20 the entire 
Battalion had arrived. 

To reduce the insect nuisance, Bikini and Enyu 
Islands were sprayed every few weeks with DDT; 



Amen and Erik were sprayed once. These precautions 
proved effective. 

Preparing moorings was a large job. The mooring 
positions had been specified several weeks in advance, 
in Washington, D. C. ; plans called for mooring bows 
and sterns of the central target ships to prevent exces- 
sive shifting: with tide and wind.* 



Technical and scientific preparations were nearly 
complete as A-Day approached. But the success of that 
day was to depend fully as much on the Force Organi- 
zation as on the Staff and Technical Organization. 

The Force Organization was responsible for oper- 
ations. After policy questions had been decided by 
the staff organization and after the technical require- 
ments had been decided by the technical men, it be- 
came the responsibility of the Force Organization to 
execute the necessary action in the field. 

The Force Organization which had been adopted 
by Admiral Blandy was designed especially to meet 
the unusual requirements of the Operation. Eight sep- 
arate Task Groups were created. 

*A typical mooring consisted of a buoy, a riser chain, a clump, 
three 10-ton anchors, and three anchor chains. The clump was a 
10-ton concrete block resting on the bottom of the lagoon. It was 
attached to the anchors by means of 500-ft. chains. The riser chain 
coymecting the buoy and the clump was made as short as feasible, 
to limit the swing of the attached target vessel. 



Task Group 1.1, the Technical Group, was com- 
manded by Rear Admiral W. S. Parsons, who was also 
Deputy Task Force Commander for Technical Direc- 
tion. The group included seven large laboratory ships, 
several radio-controlled drone boats, and LSM-60, 
which was the ship from which the B-Day bomb was 
to be suspended. 

Task Group 1.2, the Target Vessel Group, was com- 
manded by Rear Admiral F. G. Fahrion, who had also 
served as Commander of the Advance Echelon and 
Commander of all the Naval Task Groups until the 
Task Force Commander's arrival at Pearl Harbor. 
From his Task Group flagship FALL RIVER, Ad- 
miral Fahrion directed all operations of the 93 target 
vessels, including mooring them. (These vessels are 
listed in Appendix 9.) 

Task Group 1.3, the Transport Group, was com- 
manded by Captain W. P. Davis (Navy), who was re- 
sponsible for the press ship APPALACHIAN, the 
observer ships BLUE RIDGE and PANAMINT, and 
eleven other large transport ships which were to quar- 
ter and mess the target ships' crews after those ships 
had been evacuated. 

Task Group 1.4, the Army Ground Group, was led 
by Colonel J. D. Frederick. It was responsible for all 
opei-ational activities by the Army Ground Group. In- 
cluded were units drawn from the Signal Corps, Ord- 
nance Department, Chemical Corps, Quartermaster 
Corps, and Army Air Forces. Principal activity was 



exposing as many types of Army equipment as pos- 
sible to the explosions and determining the damage 

Task Group 1.5, the Army Air Group, was com- 
manded by Brigadier General R. M. Ramey. It was 
responsible for all operations by Army planes. Its Air 
Transport Unit, comprising ten C-54's each capable 
of carrjdng 54 persons, flew thousands of tons of Cross- 
roads personnel and freight between Kwajalein and 
the United States. Its Tactical Operations Unit, com- 
prising 13 B-29's, flew the bomb-carrying plane used in 
Test A and also flew weather and radiological recon- 
naissance planes. Other units operated photographic 
planes, scientific instrumentation planes, and radio, 
press, and observer planes. The Drone Unit was unique 
in aviation history; it successfully operated 6 B-17 
Flying Fortresses as drones. With no one aboard, these 
great planes were radio-guided through their pre- 
scribed flights across the target area, a unique and im- 
pressive feat.* 

*A number of Army Air Forces officials believe that the drone- 
plane program midertaken for Crossroads advanced the science 
of drone-plane operations by a year or more. To be sure, a few 
ivar iveary B-17's had been flown ivithout crews during the latter 
part of the recent war, but they and their cargoes of explosives were 
deliberately crash-landed. Also, a few B-17's had been landed by 
remote control; but pilots were aboard, ready to take over control 
in case of trouble. Operation Crossroads was the first operation in 
which take-off, flight, and landing were accomplished with no one 
aboard. The feat was an impressive one; many experts had thought 
it could never be accomplished with planes of this size. 



Their photographic and air-sampling missions were 
accomplished withont accident to any of the participat- 
ing Fortresses.* 

Task Group 1.6, the Navy Air Group, was com- 
manded by Rear Admiral C. A. F. Sprague. This group 
added to aviation history by perfecting the radio-con- 
trol of drone planes catapulted from an aircraft car- 
rier.! Such planes were used for photography and for 
collecting air samples. The Group also operated four 
helicopters, fifteen PBM patrol planes, and several 
TBM avengers for use in guiding drone boats. Activi- 
ties were based principally on the carriers SHANGRI- 

Task Group 1.7, the Surface Patrol Group, was 
commanded by Captain E. N. Parker (Navy). It was 
to play an especially large part in the radiological 
safety operations immediately following the under- 
water explosion. Test B. 

Task Group 1.8, commanded by Captain G. H. 
Lyttle (Navy), was responsible for many services, in- 

* Closest approach to an accident occurred just after the B-Day 
explosion, when one of the B-17 drones, returning to its Eniwetok 
base overran the runway and came to rest on the heach. The plane 
had been flying directly above the Zeropoint when the explosion 
occurred, and its brakes had been damaged. Fortunately, over- 
running the runway did no damage of any significance. 

t The drone planes, F6F Hellcats, were not landed on the carrier 
but on an airfield at Roi, an island of Kwajalein Atoll. Shortly 
before the A-Day explosion one of the drones went out of control 
and crashed. 


Woods Hole Oceanographic Institi^ion 


eluding repair, fueling, water, mail, provisions, recre- 
ation, hospitalization, and evacuation. 

Lines of organization were pleasantly invisible at 
Bikini. Officers and enlisted men, scientists, and ob- 
servers, became a part of the tropical scene. 

Shrill pipes called the men early each morning. 
Breakfasts were varied and substantial. Plans of the 
day were posted. Climbing from their steel- walled liv- 
ing quarters to the clean gray decks, the men gave first 
attention to the weather. Fortunately, fair weather 
and cooling breezes usually prevailed. Tuna and barra- 
cuda could occasionally be seen circling the ship. 

The clutter of small boats flanking each ship came 
to life. .Coxswains and their crews climbed out along 
booms extending over the water; they descended by 
rope ladders into the yawning boats bobbing up and 
down on the waves. They warmed up the engines, re- 
ceived megaphoned orders from the officer-of-the-deck, 
cast off, and then picked up their loads of scientists, 
technicians, and inspectors. 

By 9 :00 a.m. thousands of men had been deposited 
on the target vessels. They installed apparatus, tested 
it, and adjusted it. They put animals aboard, placed 
them in their cages, filled their reservoirs of food and 
water. They hoisted trucks, airplane sections, machine 
guns and field artillery aboard and secured them to the 
decks with steel cables running through eye-bolts. 
Boxes of pyrotechnics, canned goods, and medical sup- 
plies were taken aboard, made fast, and clearly labeled. 


Woods Hole Oceanographic Institution 


Meanwhile ships' engineers and their assistants were 
shutting down machinery and getting ready to close all 
watertight compartments. When the day of the test 
should finally arrive. 

Throughout this scene of apparent confusion pho- 
tographers and inspectors made their way, intermin- 
ably photographing everything of interest and taking 
voluminous notes on ready-made forms. No reliance 
was to be placed on memory. The aim in the tests was 
not merely success or failure, but accurately-inscribed 
data sheets by the ton which could be referred to with 
confidence in the future. 

Meanwhile force and staff conferences were being 
held on the MT. McKINLEY and good progress was 
reported.* Press conferences were held on the port deck 

Men lucky enough to receive liberty picked up their 
swimming trunks, piled into LCVP's or whale boats 
and made for Bikini beach a few miles to the north. 
They spent the afternoons swimming, playing baseball, 

* 7^ is not surprising that scientific and operational groups 
occasionally found themselves on opposing sides of discussions. Tech- 
nical men showed no embarrassment in proposing whatever changes 
of plaris would permit gathering better data. But operations men, 
anxious to avoid last-minute complications, favored standing pat. 
Because the Operation was basically a technical one, the technical 
men usually had their way. 

t Dr. R. A. Sawyer, Technical Director, brought with him to 
one of the press conferences Mr. R. S. Warner, Jr., Los Alamos 
bomb expert. He introduced Mr. Warner as "the man who will tell 
you almost anything about the bomb — except what you want to 



drinking beer and soft drinks. In the evenings they 
attended motion picture shows on deck.* Recreation 
was made as pleasant as possible. 

Rehearsals and weather dominated discussions dur- 
ing the last few days before A-Day. Many informal re- 
hearsals were carried out by the various groups sep- 
arately, and there was one full-dress rehearsal. This 
was held on Queen Day, June 24, and was completed 
with success. 

The importance of weather was far greater than 
might be expected. Naturally, clear skies were desired 
by observers and photographers. Good visibility even 
from an altitude of five or six miles was needed by the 
bombing plane; no mistake could be tolerated in its 
identifying of the brightl.y-painted Zeropoint ship, 
NEVADA. High winds might have interfered with 
bombing accuracy and drone plane operation ; unsteady 
winds might have permitted the radioactive materials 
in the air to be swept back over the support ships. Even 
though the winds might be steady at low altitudes, a 
counter current at high altitudes might have been dis- 
astrous to the support ships. But perhaps the most 
stringent requirement was that good weather be pre- 
dictable 24 hours in advance. Only on the basis of firm 
advance prediction could the great A-Day program be 
gotten underway. 

* For the 42,000 men of the Task Force, daily requirements in- 
cluded 70,000 candy bars, 40,000 ^founds of meat, 89,000 pounds of 
vegetables, 4,000 pounds of coffee, 38,000 pounds of fruit. 



Early in the morning of June 30 the weather ex- 
perts made a prediction of fair weather and favorable 
winds for the following day, which was to be A-Day. 
The word was flashed to all ships and land stations, 
and to the entire world. Scientists gave their instru- 
ments a final tuning up, test animals were placed at 
their proper locations, target vessels were closed and 
the crews were taiken off. 

By dusk the evacuation of the lagoon was well 
underway. For hours the support ships had been filing 
silently southward, out into the open sea. No longer 
was the lagoon fiUed with twinkling lights and sputter- 
ing small boats. The target vessels la}^ deserted, a dark 
cluster in front of the thin dark line of abandoned 
beaches. For several of the ships, the sun had set for 
the last time. 




The Test-A bomb exploded at exactly 34 
seconds after 9:00 a.m. on July 1, 1946, Bikini local 
time, or approximately 5 :01 p.m. June 30, 1946, East- 
ern Standard Time. 

The bomb had left Kwajalein at 5:55 a.m., aboard 
the B-29 Dave's Dream, Aircraft No. 44-27354. It had 
been loaded on the previous day. At the originally 
scheduled take-off time, 5.34 a.m., the bomber was 
standing ready and waiting. But uncertain weather 
caused a short delay; the go-ahead signal was not 
radioed from the MT. McKINLEY until 5 :40. Three 
minutes later the plane taxied towards the take-off 
position at the western end of the runway. The take- 
off itself was uneventful.* 

Climbing slowly, the bombing plane held a north- 
westerly course. It reached bombing altitude over 

* Those who climhed aboard the plane were: Maj. W. P. Swan- 
cutt, Airplane Commander; Brig. Gen. R. M. Ramey, Task 
Group 1.5 Commander; Col. W. J. BlancJiard, Air Attack Com- 
mander; Capt. W. C. Harrison, Jr. (Army), Co-Pilot; Maj. H. H. 
Wood, Bombardier ; Col. J. R. Sutherland, Bomb Commander; 
Ens. D. L. Anderson, Weaponeer; Mr. L. D. Smith, Weaponeer; 
Capt. Paul Chenchar, Jr. (Army), Radar Observer; Maj. W. B. 
Adams, Navigator; Lt. R. M. Glenn (Army), Flight Engineer; 
Corp. R. M. Modlin, Scanner; Corp. H. B. Lyons, Scanner; Tech. 



Wotho Atoll, and continued on until 8:03 a.m., when 
it arrived over Bikini Atoll. Its first practice run 
over the target was made to check wind velocity figures 
received by radio from the aerological group. 

The final practice run, a full-rehearsal run, began 
at 8 :20 a.m. A radar beacon at Bikini was picked up 
from a distance of 50 miles and was used to time the 
approach and maintain the desired course of 45 de- 
grees true. The Bomb Commander and his tw^o weapon- 
eers made last minute adjustments to bomb and bomb- 
sight. A flashing lamp on the NEVADA came into 
view; NEVADA'S high-visibility paint was clearly 
identified. The simulated practice drop was made at 
8 :31 a.m. 

The final run began at 8:50 a.m., from a distance 
of more than 50 miles. Course and altitude were held 
constant. Visibility was excellent. Within a few seconds 
of 9 :00 a.m. the bomb was released and the bombardier 
called "Bomb away, bomb away!" 

Bomb bay doors were then closed, and the plane 
made a 150 degree level turn to the left. It made a 
shallow dive, losing 1000 feet altitude while increas- 
ing speed of get-away. 

Sgt. J. W. Cothran, Radio Operator. Major Swancutt's crew had 
been chosen for the job after long training at the bombing ranges 
at Alamogordo, N.M.; Albuquerque, N.M.; and over Erik Island 
of Bikini Atoll. His crew was winner in a strenuous competition 
among many other outstanding crews. His plane was yiamed after 
Capt. David Semple, Army bombing expert and leading bombardier 
in the early competition, who was killed in a B-29 crasli m Neiv 
Mexico before the move to Kwajalein. 



During the first few seconds of the bomb's descent, 
the bomb's course was almost parallel to that of the 
plane itself, and its velocity too was essentially the 
same (roughly 300 miles per hour). The downward 
velocity of the bomb increased rapidly at this point. 

The target, enjoying its last few seconds of normal 
existence, was the most gigantic test target ever as- 
sembled. Enclosing it was the deserted circle of islands 
and reefs; beached on Bikini were: one LST, two 
LCI's, four LOT'S, five LCM's, and 6 LCYP's a total 
of eighteen landing craft. Anchored on the surface of 
the lagoon were two great PB2Y-5E Coronado sea- 

But the heart of the target area was the great fleet 
of vessels clustering about the NEVADA.* Nearest 
the NEVADA were the Japanese battleship NAGATO, 
the Japanese cruiser SAKAWA, the carrier INDE- 
PENDENCE, the cruiser PENSACOLA, the sub- 
marine SKATE, the destroyer HUGHES, the con- 
crete oil barge YO-160, and the small LCM-1. The full 
list of target vessels is given in Appendix 9. 

Just outside the Lagoon, 42,000 men lined the rails 
of their ships and waited. Nearest support ships, ten 

* Ships located very near the huU's-eye, and ships almost di- 
rectly upwind from the hull's-eye, carried light loads of fuel (10 
to 33 percent) to avoid fires which might spread and envelop the 
very closely-spaced ships. The remainder of the ships carried large 
fuel loads ranging from 50 to 95 percent of capacity. Ammunition 
loads were arranged in general accord with this same scheme. The 
loading as well as the spacing was approved hy the Joint Chiefs of 



to fifteen miles away were : APPLING, ARTEMIS, 
were fifteen to twenty-five miles away. 

Waiting aloft were airplanes, manned and un- 
manned. Nearest manned planes were Dave's Dream 
and the F-13 photographic plane, Eggleston Eight. 
Nearest drone planes were three Navy F6F drone 
planes and one Army B-17 drone plane, all at twenty 
miles. There were three more Army B-17 drone planes 
at thirty miles. 

The bomb never reached sea level. When still sev- 
eral hundred feet in the air, its special fuze came into 
action and set the uncontrolled nuclear chain reaction 
in motion. Generation after generation of fast neu- 
trons sprang to life, born out of the atoms undergoing 
fission. Each generation was much larger than its 
predecessor. The last few generations, born only a few 
millionths of a second after their remote ancestors, 
were prodigious. The number of neutrons at work ex- 
ceeded the population of the earth. 

An amount of matter no heavier than a dime was 
annihilated. But the energy release was enormous, 
being roughly 1,000,000,000,000,000,000,000 ergs. This 
was equivalent to the detonation of approximately 
20,000 tons of TNT, a weight too great to be carried 
even by the world's largest fleets of giant bombers. 



This huge quantity of free energy could not be tol- 
erated by the bomb case. The outrush of energy was so 
violent that it would be inaccurate to say that the 
bomb case cracked or even melted. It simply sprang 
outwards in all directions as though it were a gas ; indi- 
vidual atoms shot outward with speeds far exceeding 
the velocity of sound. Each atom started its trip in- 
stantaneously, and without regard to previous physical 
condition. It was literall.y ''every atom for itself" in 
the chaotic rush from the intolerable concentration of 

Atoms were not alone in their outward flight. Neu- 
trons, beta particles, and protons joined the rush. 
Mingled with them were the highly radioactive fission 

Electromagnetic radiations, too, joined the surge. 
Gamma rays of extremely great intensity started out- 
ward with the velocity of light, and ultraviolet light, 
visible light, and infrared light followed suit. These 
wave-like radiations tended to outrace the atoms and 
nuclear fragments. 

It was the visible light which gave the observers 
their first indication that the explosion had taken 
I^lace. This light, accompanied by invisible ultraviolet 
and infrared radiation, sped onward, and even at dis- 
tances as great as the moon it would have been clearly 

Let us slow down the events of the first few seconds 
after the detonation and examine each phenomenon 



closely in the light of all information now available and 
releasable. What the eye took in was relatively incon- 
seqnential, but the complete sto-ry revealed by the pha- 
lanx of instruments is a tremendous one. To analyze it 
fully will require hundreds or even thousands of man- 
years of effort by army and navy engineers. 

For simplicity, we shall use Zeropomt hereafter to 
indicate the actual position of the bomb at the instant 
of detonation (Mike Hour) ; projected Zeropoint re- 
fers to the point on the Lagoon surface directly be- 
neath the Zeropoint. 


From the detonating bomb the spherical shock wave 
in air spread rapidly. High speed cameras clocked its 
expansion. Very close to the bomb the shock wave ve- 
locity was extremely great, undoubtedly more than 
three miles per second, or 10,000 miles per hour. No 
bullet or rocket has ever approached this speed. 

Even by the end of the first tenth of a second the 
shock wave had slowed considerably. Before one sec- 
ond had passed, it struck the water and forced the 
surface down several feet throughout a wide area. The 
shock wave reflected from the surface of the water now 
joined the direct wave ; the merged wave then expanded 
at very high speed, whipping the surface of the water 
into shimmering fury. Many of the air-borne cameras 



made excellent records of the line of demarcation be- 
tween agitated water and water not yet swept. The 
shock wave buffeted every ship of the target array and, 
still traveling at velocity greater than that of sound, 
continued its outward sweep. 

After traveling three miles, the shock wave had lost 
much of its original character. Its hammer-blow qual- 
ity was less pronounced, and it took on the character 
of a sudden violent gust of wind. The automatically- 
operated motion picture cameras on Bikini showed the 
palm trees shake vigorously as the invisible wave shot 

After roughly fifty seconds the wave reached the 
support ships, located ten or more miles from the 
Zeropoint. But at this distance it was no longer a shock 
wave; it was a mere pressure wave. The wave front 
was no longer ^'square"; the velocity had subsided to 
that of sound, 1140 feet per second. This fully-tamed 
wave produced in the ears of observers only a dull, 
low-pitched thud. 

The shock wave had quitted the lagoon; but thou- 
sands of instruments bore witness to its passage, and 
five ships were sinking. 


Within five seconds an excellent, indelible record 
was obtained of peak pressure, the most important 
property of the shock wave. The majority of the gages 


had performed well. The simplest ones operated es- 
pecially well during the entire performance of the in- 
visible shock wave. 

Hundreds of gages were recovered within 48 hours. 
Recovering the gages from the GILLIAM was par- 
ticularly dramatic. GILLIAM was the ship nearest 
the Zeropoint; in fact she was the only ship within 
1000 ft. of the projected Zeropoint. She took a terrific 
beating, and sank almost immediately. Pressure ex- 
perts were most anxious to find what the pressure had 
been at this key location; they wanted to know just 
what constituted a fatal blow. Divers were put to work 
quickly. They were briefed carefully as to just what to 
look for, or rather grope for. They went down, moving 
about with great difficulty through the almost formless 
wreckage. Twice they came up to the surface to report 
failure, and twice they were briefed further and sent 
down to try again. The third attempt succeeded. They 
located the gages and brought them to the surface. 
Beaming scientists carried the gages back to the labora- 
tory ship KENNETH WHITING, cleansed them, and 
then strove to interpret their messages. No one had 
expected the bomb to explode close to GILLIAM; ac- 
cordingly the gages placed aboard her were not of a 
type intended for measuring very high pressures. Many 
of them had gone far offscale. Careful study was 
needed before the readings could be interpreted re- 



Pressure readings from all types of gages were now 
compiled, and elaborate graphs prepared. To the grati- 
fication of the experts, the graphs jibed closely with ex- 
pectations. Both the height and shape of the plotted 
curves agreed well with predictions made months be- 
fore by scientists from the Los Alamos Laboratory and 
from the Navy's Bureau of Ordnance. The accuracy, 
too, was satisfying. Although individual values often 
appeared out of line by 20 or 40 percent, when the read- 
ings of all gages at a given range had been averaged, a 
composite value of high accuracy resulted. 

Many pressure values considerably greater than 
100 pounds per square inch were successfully recorded. 
They were obtained by gages located at or just above 
the surface of the water some distance from the pro- 
jected Zeropoint. Unfortunately, there was no gage 
located exactly at the projected Zeropoint; but esti- 
mates indicate that the pressure there was extremely 
great — expressible in hundreds or thousands of pounds 
per square inch. At greater distances, pressure values 
were, of course, smaller; at ranges of 2000 to 3000 
yards, for example, the pressure was well below ten 
pounds per square inch. The radiosonde-type pressure 
gages parachuted from planes at ranges of six or eight 
miles performed well. Their radioed messages were re- 
ceived, recorded, and analyzed. Their pressure values, 
amounting to only a small fraction of a pound per 
square inch, were in excellent agreement with one 



Pressures inside gun turrets and ship compartments 
were small, seldom exceeding a few pounds per square 
inch. The data obtained were sufficiently extensive to 
form a firm basis foi- determining where crew members 
would have been safe from the ]:)last, and where ad- 
ditional protection would have been needed to insure 

There were, of course, many failures among the 
thousands of pressure gages used. Some of those which 
were to be started by radio were started too late as a 
result of a timing signal failure.* Others operated 
badly as a result of imperfect adjustment of the gages 
themselves or of ''black box" starting mechanisms. 
Some gages found themselves unexpectedly close to the 
Zeropoint and gave undecipherable off-scale readings; 
others were unexpectedly far from the Zeropoint and 
gave no response whatever. Many gages sank with 
the five mortally- wounded ships they were mounted on ; 
few of these gages were recovered. Some of the gages 
were shielded by ships' superstructures and gave ab- 
normally low readings; in some instances the inter- 

* Arrangements had heen made to send out a master timing sig- 
nal, which was to start a number of recording instruments an in- 
stant before the explosion occurred. Actually, the sigyial was sent 
out a number of seconds too late. This delay was caused partly by 
imperfect receptiori of a preliminary radio signal and partly by 
human error. Plans were such that nothing short of this coinci- 
dence of ill luck could have thrown off the master signal. The great 
majority of instriiments were not dependent on this signal, and the 
multiplicity of instrurnents was such that all principal types of 
information sought were achieved despite inoperativeness of indi- 
vidual groups of instruments. 



ference produced abnormally high readmgs.* Oddly 
enough, one of the most valual^le of all the pressure 
results was that obtained from a specially-mounted beer 
can, whose graceless collapse filled an otherwise serious 
gap in the pressure story. 


The measurement of impulse, although less satis- 
factory than the measurement of pressure, was entirely 
adequate. Despite the timing signal failure mentioned 
previously, a number of good records of pressure-ver- 
sus-time were obtained. From these, by the usual 
method of integrating, physicists computed the impulse 
values. As expected, the net impulse was practically nil 
except extremely close to the Zeropoint. At greater 
ranges the impulse delivered by the positive pressure 
phase was almost exactly counterbalanced by the nega- 
tive phase, which started one-half to one second later. 

But even though the net impulse was practically nil 
at most of the target vessels, the net effect was far 
from nil. It was, of course, the impulse during the posi- 
tive phase which was responsible for the majority of 

^Although the homh detonated at approximately the planned 
altitude, its plan-view position was 1500 to 2000 ft. to the ivest of 
the intended hull's-eye ship NEVADA. How this discrepancy oc- 
curred has been the subject of long study; but no answer has bee^i 
found. Incontrovertible evidence is available to disprove each of the 
dozen different hypotheses which may be advanced as explanation. 
No discrepancy of anything like this magnitude occurred in the 
long series of practice drops made. 



the havoc wrought. Many masts, for example, were 
bent by this positive phase; and they certainly were 
not straightened out again by the ensuing negative 
(suction) phase. Impulse values — and ship damage 
— were particularly great because both the pressure 
and the duration of the positive phase are exceptionally 
great in atomic bomb explosions. Destruction was far 
greater than would have resulted from high pressure 
alone, or long duration alone. The bomb reaped double 


The shock wave was not visible to the naked eye; 
but the progress of the ensuing suction was apparent 
enough. Racing closely on the heels of the fast-spread- 
ing shock wave, the suction wave had the form of a thin 
shell of rarefied air. Because this air was rarefied and 
thus cooled, the water molecules present condensed in 
myriad tiny droplets, millions of them in each cubic 

The result was the formation of a large zone of fog, 
called the condensation cloud. Some persons referred 
to it as the "Wilson Cloud," in honor of C. T. R. "Wil- 
son, who fifty years ago pioneered the study of fog and 
rain, and made thousands of experiments in which fogs 
were produced by sudden expansion of saturated vapor. 

From a distance, the condensation cloud at first re- 
sembled a white hemisphere, dazzlingly bright, resting 
on the surface of the water. The hemisphere grew rap- 



idly, of course, in accordance with the velocity of the 
suction wave. Thus its diameter increased initially at 
the rate of several thousand miles per hour ; later, the 
increase proceeded at the more modest rate of about 
780 miles per hour, the velocity of sound. 

But this great hemisphere lasted only a few sec- 
onds. Its interior was rapidly burnt out by the trillion- 
watt fireball located at the center. Upward growth of 
the cloud was limited principally by too-low humidity 
in the upper strata of air ; lateral growth was limited 
by the gradual dying off of the suction wave. The 
myriad droplets were evaporating fast. Within five sec- 
onds the cloud had become a great horizontal ring two 
miles in diameter, resting on the water and enclosing 
the fireball. In another five seconds the ring had dis- 
integrated; only patches of cloud remained. 


The fireball, unlike the condensation cloud, was 
no mere spectacle. It dealt serious injury to ships and 
test animals. Beginning its existence in the very proc- 
ess of distintegration of the bomb, it was of indescrib- 
able brightness during the first two seconds. Then, for 
about three seconds, it was obscured by the condensation 
cloud. At about five to eight seconds after Mike Hour 
it came back into view again. It grew, swept rapidly 
upward, and by ten to twenty seconds after Mike Hour 



the fireball had lost itself in the rapidly rising mush- 
room cloud. 

The fireball's real punch occurred within the first 
half second. In this brief interval an appreciable frac- 
tion of the total energy released by the bomb sped out- 
ward at the velocity of 186,000 miles per second. It was 
in this interval that fiash burns were produced on 
target equipment and animals. 

The initial output of optical radiation was hundreds 
of trillions of watts, greater than the aggregate power 
output of all the electric light bulbs ever manufactured 
by man. 

In the first few tenths of a second the fireball grew 
very rapidly. As it grew, each square inch of its sur- 
face became less brilliant, but there were, of course, 
more square inches in its surface. Accordingly, the 
total output of light decreased according to a somewhat 
complicated formula. Aerial photographs, analyzed 
with the help of densitometers, were particularly valu- 
able in following the detailed course of this split-second 

Photometrists found that the greatest surface tem- 
perature of the fireball was well above 100,000 degrees 
Fahrenheit. Interior temperatures were far higher. 
To observers 10 miles away, the illumination pro- 
duced per square inch of fireball area was several times 
that of the sun at noon. The fireball produced a bluer 
light than the sun, which again indicates the fireball's 
greater intensity. 



Although the fireball itself was rich in ultraviolet 
light, including light of the ''vacuum ultraviolet" re- 
gion, much of this light was cut off from observers by 
the intervening atmosphere. Practically no light of 
wavelengths less than 3000 Angstrom units was de- 
tected near sea level at ranges of twenty miles. Much 
infrared light was detected, although here again ab- 
sorption by the atmosphere was severe. The water vapor 
content of the atmosphere was of course great, and such 
vapor is well known for its reluctance to transmit 
infrared light. 


The mushroom, now the common sjaiibol of the 
atomic age, was far more spectacular than any still 
photograph can suggest. Its height and statuesque 
beauty were impressive ; but even more impressive was 
the speed of its writhing upward surge. 

The speed of its ascent is understandable enough. 
When the bomb exploded, Avhite hot gases instantly 
spread and filled a region about one-third of a mile in 
diameter. But these gases were ver}^ thin ; their aggre- 
gate weight was extremely slight — about the same, in 
fact, as the weight of a hydrogen-filled balloon of equal 
diameter. Now a hydrogen-filled balloon of this fan- 
tastic size would have enough lift to raise tJwusands of 
tons. Such, then, was the magnitude of the buoyant 
force urging the fireball upward. 


Crew of the submarine rescue vessel WIDGEON watch the test sub- 
merging of the submarine APOGON. The submerging operation was 
difficult; never before had there been occasion to submerge a sub- 
marine without crew aboard. The method used was to fill part of the 
ballast tanks with water, then suspend heavy weights from the bow 
and stern by cables of carefully chosen length. These weights over- 
came the submarine's residual buoyancy and drew her down to the 
desired depth. She could be surfaced again by pumping air back into 

her ballast tanks. 

Plate 17 

UPPER. Test A, the explosion in air; 9:00 a.m. on July 1, 1946. The 

hemispherical condensation cloud, lit by the white-hot fireball at the 

center, outshines the tropical sun. LOWER. The fireball starts its swift 

ascent into the stratosphere. 

Plate 18 

Plat© 19 

The mushroom growing out of the Test A explosion in air has now 
reached an altitude of five miles. Veiling the mushroom top is the ice 
cap, or scarf cloud, believed to be composed of myriad tiny ice crystals. 
The mushroom itself is a mixture of vapor, smoke, soot, and rqdioactiv? 

fission products. 

Pht§ 20 

The light carrier INDEPENDENCE, located between 1000 feet and V2 
mile from the projected Zeropoint, shows severe damage. Her 600 
foot flight deck is broken in several places. Part of the deck planking 
has burned. Her four stacks have been demolished, and her antenna 
masts are bent or broken. 

quarter, being nearest to 
the Zeropoint, took the 
worst beating; much of 
the wreckage here was 
unrecognizable. A fire 
broke out on the hangar 
deck, adding to the dam- 
age already done by the 
shock wave. Huge beams 
of heavy gage steel had 
been ripped loose. The 
plating above the water- 
line was damaged over a 
considerable area. 

Plate 2 

A monitor from the Ra- 
dioactivity Group uses a 
Geiger counter to meas- 
ure the radioactivity on 
the SKATE. This subma- 
rine, of modern heavy 
construction, v^as located 
v/ithin 1/2 mile of the Test 
A Zeropoint. Being fully 
surfaced, she took ter- 
rific punishment. Most of 
her superstructure was 
stripped off, exposing a 
large area of her pres- 
sure hull. 

General view of damage produced on the submarine SKATE in Test A. 
Her conning tower fairwater was badly smashed, and her bridge also. 
Periscope and radar shears were bent. Inside her pressure hull, how- 
ever, damage was not severe; within three days she made a successful 
surface run under her own power. 

Plate 22 

Battered almost beyond 
recognition is this Navy 
seaplane which had been 
placed on the stern of the 
battleship NEVADA, lo- 
cated 1500 to 2000 feet 
from the Test A actual 
Zeropoint. Besides pro- 
ducing mechanical dam- 
age, the explosion caused 
fires in combustible ma- 
terials at distances as 
great as one or two 
miles. Various other ma- 
terials were melted or 
scorched. Army quarter- 
master stores proved to 
be especially vulnerable. 

The NEVADA, bull's-eye 
battleship, escaped v/ith 
moderate damage. The 
bomb, instead of deto- 
nating directly above her, 
detonated 1500 to 2000 
reet away. NEVADA'S 
Iwo topmasts failed, and 
the starboard yardarm 
also. Her weather deck 
was dished moderately. 
Some stanchions and 
bulkheads were distorted. 
However, her hull was 
practically undamaged, 
and her interior was little 
disturbed. The deck- 
loaded gear suffered 

Plate 23 

,fiiii*>rf'1i^ mtfft^^ 

UPPER. Insidious almost be- 
yond belief, the great mush- 
room cloud conjured in Test A 
harbored radioactive fission 
products equivalent to hun- 
dreds of tons of radium. 
Manned planes v/ere kept 
miles away, but drone planes 
v/ere guided directly through 
the cloud, sampling its content 
v^ith the aid of filters mounted 
in boxes attached to the under- 
sides of the planes' wings. Re- 
moving the filters was done 
with great care. LOWER. A 
radioactivity check is made on 
a goat exposed to the Test A 

Plate 24 


The fireball rose initially at a rate of more than one 
hundred miles per hour. Within twenty seconds it 
transformed itself into the fireless head of the mush- 
room, now one mile high. Two minutes later the mush- 
room's altitude was five miles; five minutes later it 
was seven miles, one mile higher than Mt. Everest. 

As the mushroom head rose at express-train speed, 
it sucked air in beneath it. Scooped up in this turbulent 
trailing festoon, called the stem, were soot from the 
stacks of the nearer target vessels, smoke from the 
flash-burned decks and equipment, and water vapor.* 

The mushroom head broadened as it rose; event- 
ually it attained a width of nearly two miles. The air 
rising in the mushroom head became cooler as it rose 
and expanded; air pushed upw^ard just above the 
mushroom head was cooled also. This cooling resulted, 
of course, in condensation. A remarkable phenomenon 
occurred: a thin white cap or scarf cloud appeared 
lying just above the mushroom top and cleanly sep- 
arated from it. It is probable, although not certain, 
that this consisted not of water droplets but of very 

* The mushroom contained also various unusual gases created hy 
the bomb's ionizing radiations. These radiations were partially ab- 
sorbed by the nitrogen and oxygen molecules of the air and the 
result was: nitrogen molecules were broken up into individual 
nitrogen atoms; and the oxygen molecules were broken into indi- 
vidual oxygen atoms. When the unmated nitrogen and oxygen atoms 
collided, they immediately joined to form molecules containing 
oxygen and nitrogen together. Such molecules have an apricot 
color, and traces of this color were clearly visible in the A-Day 



small ice crystals. Sucli an ice-cap, never before pro- 
duced by man, can only form when the meteorological 
conditions are exactly right. 

The mushroom did no damage, but it was far more 
fearsome than its soft white form could suggest. In it 
were shrouded the bomb 's deadly fission products ; for 
in such a ''self -cleansing" explosion as this, nearly all 
the bomb products remain in the air and are carried 
aloft in the mushroom. The amount of radioactive 
fission products infesting the cloud was small in terms 
of weight. But its potency was impressive, being tem- 
porarily equivalent to hundreds of tons of radium. 
(The world's total supply of concentrated radium 
amounts to only a few pounds.) If an aviator had flown 
through the mushroom and inhaled its air, he would 
probably have died as a result. If an aviator's plane 
had failed and he had been forced to jump, his para- 
chute w^ould have been of little avail if it carried him 
into this cloud. 

The mushroom's menace was a lingering one. Its 
fission products settled out very slowly, endangering 
everything lying in its path. The menace became the 
more insidious when, about one hour after the explo- 
sion, the cloud lost its characteristic shape and became 
visually indistinguishable from other clouds in the 

Airmen continued to track it for many hours in 
B-29 planes carrying Geiger counters ; they found that 
the affected air region followed the course predicted 



by the aerologists, and that only deserted ocean areas 
received the continuous and invisible fall-out of radio- 
active materials. 

Fortunately, the contaminated region healed itself 
relatively promptly. The fission products themselves 
lost a large fraction of their potency in a matter of 
hours, and lateral and vertical mixing with unaffected 
air proceeded rapidly. Within a short period the ma- 
terials were dispersed throughout thousands of cubic 
miles of air. The materials were now so extremely dilute 
as to be harmless. Nevertheless, various scientific 
groups in America and in Europe are reported in the 
newspapers as having detected slight changes in the 
radioactivity in the atmosphere some days after the 
explosion. There is no doubt that, like the ashes thrown 
into the air in the explosion of the Krakatao many years 
ago, the fission products circled the globe for many 


Gamma radiation dominated the repertory of nu- 
clear radiations. Alpha particles, beta particles, and 
neutrons were, of course, produced in abundance, but 
being light particles they were rather effectively 
blocked or slowed by collision with atoms in the air. 
Many of them failed to penetrate more than ten or a 
hundred feet of air; few of them reached beyond the 
innermost target vessels. And even on these vessels 
their effects were of questionable importance in view 



of the great damage caused by the shock wave, heat 
flash, and gamma radiation. 

The gamma radiation's maximum power was dis- 
played in the periods of a few seconds. Geiger count- 
ers on target vessels demonstrated that an enormous 
burst of gamma radiation was produced during the 
instant when the bomb was detonating; additional 
gamma radiation came from the fission products in the 
fireball. But after the mushroom had borne its poison- 
ous pall to high altitude the gamma radiation at sea 
level was very weak indeed. 

The total amount of gamma radiation reaching the 
target vessels was large. In many instances the photo- 
graphic film gages showed aggregate dosages of the 
order of hundreds or thousands of roentgens.* The 
total output of gamma radiation was so great that if 
by some feat of magic it could have been distributed 
uniformly among several million persons it would have 
eventually killed or seriously injured all of them. Of 
course, in any practical situation the number of per- 
sons affected would be very much smaller. 

The gamma radiation was of many wavelengths, 
covering an appreciable spectral band. The typical 

* The roentgen is a unit of cumulative intensity of ionizing 
nuclear radiation. Radiation which is sufficiently intense and pro- 
longed to produce a hillion ion pairs in a single cubic centimeter 
of air represents approximately one roentgen. One tenth of a 
roentgen was adopted hy Joint Task Force One as the maxijnum 
safe dosage per day. Fifty or 100 roentgens per day can he seri- 
ously harmful to man, and a few hundreds roentgens may prove 



wavelength was roughly one ten-billionth of a centi- 
meter; 25,000,000,000 such waves would be required 
to cover one inch. The energies of the individual gamma 
ray photons, being in exact inverse proportion to the 
wavelength, were tremendous. A typical photon had 
an energy of about one million electron volts. The high 
energy of these photons meant that they had great 
penetrating power — greater than that of typical X- 
rays. In practical terms this meant that no ordinary 
screen of steel, lead, or other material known to man 
could successfully block off the radiation. Very heavy 
steel walls, several inches thick, would reduce the in- 
tensity by an appreciable factor and foot-thick steel 
walls would reduce the intensity to a fraction of the 
original value. But in the face of such extremely in- 
tense radiation as that which struck the target ships, 
even a fraction of the initial intensity might do serious 
and lasting harm. 

To compute the total potential effectiveness of nu- 
clear radiations on ships' crews has not proved to be 
easy. To be fully meaningful, such computations must 
take into account many factors. The most obvious of 
these factors is the distance of the ship from the Zero- 
lioint. All radiations are, of course, less intense at 
greater distances and are therefore less effective there. 
But the situation is complicated; the decrease in in- 
tensity of some kinds of radiation is much more pro- 
nounced than for others. Even fast and slow neutrons 
show unlike deference to distance. Gamma rays too 



are not of uniform behavior. For each distance of in- 
terest, it is necessary to compute separately each radia- 
tion's effectiveness, and then to combine the results 
to obtain a measure of the total effectiveness. Another 
important factor is the altitude of the Zeropoint. Ob- 
viously, if the bomb detonates almost at the surface 
of the ocean, the radiation will probably enter the ship 
through the side, and persons well below the waterline 
may be almost perfectly protected by the intervening- 
water. But if the bomb detonates directly overhead, 
the thickness of the decks will be of principal impor- 
tance. The type of ship, too, makes a difference. Thick- 
walled battleships must be expected to give far greater 
protection than thin-walled destroyers. The distribu- 
tion of the men throughout the ship must be considered 
too. Persons far below decks may escape relatively 
lightly even when persons exposed topside receive fatal 
doses. In a later section the attempt is made to state 
the over-all effect of nuclear radiation on ships' per- 

No one knows what psychic catastrophe the gamma 
radiation might wreak on the doomed crews. The ra- 
diation can claim these remorseless attributes : it is 
invisible, so that no one can see it coming; ordinarj^ 
walls do not stop it, so that ''no hiding place down 
here" applies all too fully; medical science knows of 
no way to save severely exposed persons; and the ra- 
diation produces no immediately apparent effect, so 
that overly apprehensive persons entirely out of range 



may be convinced death is at hand. This last factor is 
probably more important than it logically should be 
since persons almost always overestimate the closeness 
of explosions. Explosions a considerable distance away 
may somid next door. 


The fact that five ships were sunk by the A-Day 
explosion is of little absolute importance. The num- 
ber might have been considerably greater or less, de- 
pending on exactly where the bomb exploded and on 
the exact disposition of the ships. 

Damage to ships should be evaluated in the light 
of their locations. Rough indication of the locations 
with respect to the bulls-eye ship NEVADA is pro- 
vided by Figure 4. Approximately twenty of the target 
ships were located within the central area of one square 
mile. Many of the other ships were spaced along 
radiating lines or spokes. These lines were curved 
slightly, so that the inner ships could not shield their 
outer neighbors. 

The majority of the ships carried considerable loads 
of fuel and ammunition. Thus secondary effects, such 
as fires and ammunition explosions, were evaluated 
as well as the primary effects. Ships in the upwind 
sector, however, carried only very small loads of fuel. 
These loads were kept small so that, in the event that 
the fuel caught fire and spilled out onto the Lagoon 



Fig. 4. Test A Target Array. 



surface, it could not envelop scores of other ships, con- 
suming them and their important cargoes of test ani- 
mals and instruments. Such danger was heightened, 
of course, by the abnormally close spacing of the ships. 

What struck the ships first? Undoubtedly it was 
the thermal radiation and the gamma radiation. These 
struck the ships within the first thousandth of a second. 
The thermal radiation lasted only a few seconds, ceas- 
ing with the extinction of the fireball. The gamma radi- 
ation was greatly reduced in intensity as soon as the 
mushroom got underway in its climb to the strato- 
sphere. The thermal radiation produced serious effects 
on exposed test animals and on various kinds of ship 
equipment, but it produced very little serious damage 
to ships' hulls and superstructures. Gamma radiation 
likewise had relatively little effect on ship structures. 

The shock wave did the damage. The impulse it 
delivered, with its extraordinarily high peak pressures 
and its long-lasting positive pressure phase, was irre- 
sistible on the nearest ships. It bent masts, depressed 
decks, crumpled stacks, unseated cranes, dished side 
plating. It twisted and broke the flight deck of the 
nearer aircraft carrier and ripped nearly all the super- 
structure off a surfaced submarine nearby. 

Detailed surveys of damage had to wait until the 
mammoth re-entry maneuver had been accomplished. 

Drone planes were first to make close approach to 
the target center. Only eight minutes after Mike Hour 
a B-17 drone entered the mushroom at 24,000 feet. A 



few minutes later three other B-17's swung across at 
altitudes of 30,000, 18,000 and 13,000 feet. Three F6F 
drones made transits at 20,000, 15,000 and 10,000 feet. 
The planes collected air samples and returned to base ; 
their samples were sent to Kwajalein for radiological 

Four TBM planes were launched from SAIDOR a 
few minutes after Mike Hour. They obtained valuable 
photographs of sinking ships, but their main job was 
to assist the controlling of drone boats soon to be 
launched. No manned planes flew directly over the 
Zeropoint until four hours after Mike Hour. 

The LVCP drone boats started towards the target 
array forty-four minutes after Mike Hour. Their 
progress was controlled by radio signals sent from 
BEGOR, which lay just outside the long Bikini-Enyu 
reef. The leading LCVP reached the target center in 
one hour, and picked up water samples. Two hours 
later these samples had been put aboard the destroyer 
MO ALE, which was soon speeding to Kwajalein where 
the samples were to be analyzed. 

Manned boats first re-entered the Lagoon two hours 
after Mike Hour. First to enter were the six PGM's 
of the radiological safety party. A little later, twenty 
LCPL's entered also. These boats cautiously threaded 
their way throughout the target area, using their 
Geiger counters to detect any unsafe areas. Few such 
''hot" or "Geiger sour" areas were found by this 
patrol party. 



The salvage vessels now entered the lagoon and went 
to work to put out fires on several of the target ships. 

At 2 :30 p.m. the Task Force Commander announced 
over his radio circuits that the lagoon w^as safe for 
entrance by all vessels. Ships of the Technical Group 
entered almost at once. The flagship MT. McKINLEY 
entered a few minutes later, and the other ships fol- 

By sundown, eighteen of the target ships had l)een 
reboarded by special boarding teams, although regular 
ships' teams were not put aboard until later. Many 
animals were recovered and transferred to BURLE- 
SON; a number of scientific instruments were recov- 
ered also. 

In the following few days the remaining animals 
and instruments were recovered. While these were 
being studied, diving and salvage operations were 
rushed. An unsuccessful attempt was made to beach 
the Japanese cruiser SAKAWA, which was afire for 
24 hours. Soon after she was taken in tow, she keeled 
over to port and sank by the stern. The aircraft carrier 
INDEPENDENCE and the concrete oil barge YO- 
160, both badly damaged, were moved to more appro- 
priate berths. The submarine SKATE was beached in 
shallow water off Enyu Island. 

Inspection teams now swarmed over the ships, ex- 
amining every damaged item. The special data forms, 
printed long in advance, proved their worth. They in- 
sured orderly and thorough inspection, and the re- 



cording of results in a consistently uniform manner.* 
Six days after A-Day the staff of the Director of 
Ship Material completed an 85-page provisional re- 
port on damage to ships and animals. Within thirty 
days this group had completed an interim report of 
2000 pages. Five months later it had finished a monu- 
mental report of 150 volumes. The full story is now 
available as to the damage wrought in the five seconds 
after the detonation on A-Day. 

The GrILLIAM, closest of all the target ships, and 
only ship located within 1000 ft. of the projected Zero- 
point sank within one minute. She was a merchant- 
type attack transport and was 446 feet long. Divers 
later found that her superstructure was smashed al- 
most beyond recognition, and her hull also was utterly 
wrecked. She proved beyond the slightest doubt that 
a ship of this type could not hope to stand up against 
the atomic bomb at close range. 

The ANDERSON, a 338-foot destroyer located be- 
tween 1000 ft. and one-half mile, sank within eight 
minutes. Pictures taken from a PBM photographic 

* The difficulty of this job is hard to appreciate. On a single 
ship such as the INDEPENDENCE, for example, there were liter- 
ally thousands of compartments, rooms, and installations to inspect. 
Hundreds of the rooms showed severe damage, and hundreds more 
showed light damage. On the flight and hangar decks, too, there 
were enormous areas of wreckage. Merely classifying an area as 
''wrecked" or "partially wrecked" would have been relatively 
easy; hut to describe the wreckage in detail, and in terms suitable 
for later practical use by engineers, ordnance experts, commMnica- 
tions men, medical men, fire control personnel, and naval archi- 
tects, was truly a Herculean task. 



plane show her visible through the smoke cloud one 
minute after Mike Hour. Much of the upper part 
of her superstructure was missing entirely. A fire 
was burning amidships. A minute later the fire ap- 
peared to be growing in intensity and to be spreading 
aft along the port side. Still later, the fire amidships 
increased markedly, and the entire central section of 
the ship was in flames. She began to list ; within four 
minutes of Mike Hour she was on her beam ends. A 
cloud intervened for a few seconds, after which she 
was found to have rolled still further on her port side. 
Her fires now appeared extinguished, but she was 
settling fast. By six minutes after Mike Hour only a 
small portion of her bottom was visible, and in another 
two minutes she was gone. 

Divers later found her resting on her side in about 
200 feet of water. They made an extensive survey of 
her smashed superstructure and confirmed that much 
of it was missing or unrecognizable. Her deck was in 
very bad condition, and her shell plating also. 

The CARLISLE, an attack transport much like 
the GILLIAM, sank within forty minutes. She too 
was within one-half mile of the projected Zeropoint. 
Divers found her lying nearly upright, with about five 
degrees list to port. Her condition was generally sim- 
ilar to that of the ANDERSON. 

The LAMSON, a 344-foot destroyer, located within 
one-half mile of the projected Zeropoint, sank within 
eight hours. Early photographs showed her listing to 



starboard with bridge structure badly smashed. Guns 
were visible, but the mast and other light structures 
were missing. Observers airborne in PBM Charlie 
found the ship lying over on her starboard side about 
forty-five minutes after Mike Hour ; her bridge struc- 
ture was underwater and the port side of her bottom 
was above the surface. Later she floated bottom up for 
a short while, and then sank. Divers reported her 
condition as being much like that of the ANDERSON. 

The Japanese light cruiser SAKAWA, located 
within one-half mile of the projected Zeropoint, sank 
in mid-morning on the day after the explosion. A 
severe fire burned in her stern for nearly twenty-four 
hours. She showed severe structural damage topside. 
Her hull too suffered major damage; her stern was 
breached in several places. Water entered steadil^y, and 
her draft increased seriously. Despite difficult radio- 
logical conditions prevailing, the attempt was made 
to tow her to a nearby beach. But by this time her stern 
was awash and her stability had been reduced to the 
vanishing point. Soon after being taken in tow she 
keeled over to port at an angle of 85 degrees and sank 
by the stern. 

Sinkings made headlines, but it was the surviving 
ships which provided the largest amount of precise in- 
formation. The light carrier INDEPENDENCE, lo- 
cated between 1000 ft. and one-half mile from the 
projected Zeropoint, showed perhaps the most strik- 
ing damage. Her 600-foot long flight deck was broken 



in several places and badly buckled. The port corner 
of the flight deck was blown oft'. Part of the deck 
planking was burned away. All four stacks were de- 
molished, the flight deck crane was knocked over, and 
both airplane elevator platforms were blown overboard. 
Antenna masts were bent or broken. A fire broke out 
on the hangar deck, adding to the wreckage already 
produced by the shock wave. Huge vertical beams of 
heavy gage steel had been ripped loose; in some 
instances they w^ere left hanging in grotesque array. 
Her plating above the waterline was damaged over a 
considerable area, and holes were blown in the sides 
enclosing the hangar deck. Huge wrinkles disfigured 
her starboard side. Her interior showed extensive 
damage also. Her port quarter, being nearest to the 
Zeropoint, took the worst beating ; much of the wreck- 
age here was unrecognizable. 

The submarine SKATE, over 300 feet long and of 
modern heavy construction, was located within one- 
half mile of the projected Zeropoint. She was on the 
surface, and as a result lost nearly all her superstruc- 
ture. The conning tower f airwater and the bridge were 
badly damaged; the same was true of the weather 
deck along most of her length. The periscope and radar 
shears were bent to starboard. Aft of the conning tower 
most of the decking, the majority of the free-fiooding 
superstructure, and many pipes and fittings were bent, 
smashed, or even blown over the side. The bridge struc- 
ture was folded together upon itself in front of the 



conning tower. Nearl}^ half of the superstructure for- 
ward was wrecked. The side lights were shattered and 
the stern light was missing. The after windlass was in- 
operable. Inside the pressure hull, however, damage 
was not severe ; within three days she made a success- 
ful surface run under her own power. Submerging 
would have been unsafe, and was not attempted. 

The ARKANSAS, oldest battleship of the United 
States Fleet, was one of the three major combatant 
ships within one-half mile of the Zeropoint. She suf- 
fered heavy damage. When the lagoon was first re- 
entered, she was still sending up clouds of smoke from 
smouldering fires on her decks. But the shock wave 
did the most damage. Stacks, masts, and mast support- 
ing structures suffered, as well as pipe rails, bulwarks, 
stowage spaces. Much dishing occurred. Mam" doors, 
stanchions, and bulkheads were ])adly damaged. AR- 
KANSAS was defuiitely put out of action and would 
have required extensive repairs at a principal naval 

The NEVADA, bull's-eye battleship, escaped with 
moderate damage. The bomb, instead of detonating di- 
rectly above her, detonated 1500 to 2000 feet away. 
Both topmasts failed, and the starboard yardarm 
also. The weather deck was dished moderately. Some 
stanchions and bulkheads were distorted. Painted sur- 
faces on exposed parts of the superstructure were 
blackened. However, her hull was practically undam- 
aged, and her interior was little disturbed. 



The CRITTENDEN, another 426-foot merchant- 
type attack transport, received heavy damage of the 
same general type described in the previous paragraph. 

Other ships badly mauled were : the cruisers SALT 
LAKE CITY and PENSACOLA, and the destroyers 
HUGHES and RHIND. The concrete oil barge YO- 
160 suffered lesser damage, and significant damage was 
suffered by the aircraft carrier SARATOGA, the de- 
stroyer TALBOT, the concrete drydock ARI)C-13, the 
merchant-type attack transport DAWSON, and LST- 
52. Among the other ships suffering negligible to mod- 
erate damage were the ])attleships NEW YORK and 


How was the wealth of ship-damage data to be 
summarized ? This question puzzled Admiral Parsons ' 
technical experts from the outset. Various schemes 
were proposed for synthesizing the almost endless 
stream of data into simple generalizations. It would 
be convenient to be able to say: '^ Ships are sunk at 
ranges as great as X yards, badly damaged out to Y 
yards, and slightly damaged out to Z yards." But it 
was recognized from the outset that no such simple 
rules could be expected. Each type of ship has a dif- 
ferent vulnerability; and even within a single type of 
ship, newer ships may not be of the same vulnerability 
as older ships. Ship aspect, too, must be important. A 



ship caught broadside might be capsized where a bow- 
on ship might remain upright. 

Almost endless complications arise when a definition 
of damage is sought. In the midst of a battle, the im- 
portant damage is that which prevents the ship from 
fighting with full effectiveness. Here damage means 
loss of fighting efficiency. Mere loss of a rudder or 
failure of the radar sets may be regarded by combat 
crews as disastrous damage. 

When the crippled ship limps into port, damage 
means something quite different. It is expressed in 
weeks to get the ship hack into action. Thus shipyard 
engineers classify any damage as light if repairs can 
be completed in a few days. 

Foremen rate damage in terms of man-hours to re- 
pair the ship ; accountants express damage in terms of 

From the scientific point of view, damage is a meas- 
ure of how many parts are injured, and how elaborate 
the injuries are. Of no concern here is the matter of 
importance of the parts, or the time needed to repair 
them. Some persons may be interested principally in 
damage to ship's machinery or electronic equipment; 
other persons may regard damage to guns and hull as 
especially vital. 

A nice question is whether radioactivity on the 
target ships represents damage to the ships or injury 
to the crews. The ships are contaminated, but it is the 
crews which suffer. 



Now the loss of fighting efficiency concept of dam- 
age is certainly of very great importance. But it is 
hard to define exactly. Failure of main turrets might 
constitute serious loss of fighting efficiency in action 
against surface ships, but it would have no bearing on 
fighting enemy planes. Loss of radar is almost fatal in 
a battle fought on a cloudy night, but it is far less 
serious in a battle fought in brilliant sunshine. Loss 
of speed may be only of minor importance on some 
operations, and fatal in others. Another difficulty is 
duration of loss of fighting efficiency. How can we 
compare permanent loss of speed or fire-power with 
loss which can be repaired in an hour or two by the 
ship 's crew ? We can answer this only if we know how 
long the battle is to last. 

The solution adopted was to use several of these 
damage concepts in parallel. Rough definitions were 
drawn up, and the individual data were sorted out 
accordingly. Totals were compiled, and the conclusions 
came into view. 

Some major conclusions are these: 

, 1. The majority of lighter warships located 
within a critical radius somewhat less than 
one-half mile away may be expected to be 
sunk by an atomic bombing attack such as 
that executed on A-Da}^ 

2. Heavy warships located within one-half 
mile may survive, but their superstruc- 
tures will be badly damaged and the ships 
will be put out of action ; extensive repairs 



at a principal naval base will be required. 

Ships more than three-fourths of a mile 
away may suffer damage, but the damage 
will be relatively light in typical cases. 

Among the most badly damaged ships, 
damage to superstructures was very se- 
vere; hulls escaped relatively lightly. 
Damage extends to nearly all kinds of me- 
chanical and electrical equipment. 


Ships' decks, the only platforms in the neighbor- 
hood of the Zeropoint, had been generously covered 
with special test equipment of nearly every imaginable 
kind. Colonel J. D. Frederick's DSM Army Cround 
Group had exposed equipment lent by all principal 
branches of the Army, including the Air Forces, Engi- 
neer Corps, Signal Corps, Ordnance Department, 
Chemical Corps, and Quartermaster Corps. Much 
Navy equipment was exposed also, principally by the 
DSM Ordnance Group under Captain E. B. Mott, the 
DSM Aeronautics Group under Captain T. C. Lonn- 
quest, the DSM Electronics Group under Captain C. L. 
Engelman, and the relatively small DSM Supplies and 
Accounts Group. So extensive was the equipment that 
seven volumes of several hundred pages each were re- 
quired to summarize the results obtained. 



Some of the heavier items exposed were tanks, 
weapon carriers, trucks, amphibious clucks (or 
DUKWs), tractors, airplanes. Lighter items included 
guns, mortars, rocket launchers, rifles, torpedoes, mines, 
depth charges, bombs, fuzes, grenades, rockets, flares, 
telescopes, periscopes, infrared snooperscopes, alti- 
meters, fire extinguishers, water distillation equip- 
ment, odographs, knives, watches, telephones, switches, 
gas maslvs, flasks, samples of oil, grease, gasoline. Lists 
of clothing and supplies samples are almost endless; 
they included canned apples, apricots, tomato juice, 
string beans, creamed corn, bacon, turkey, butter. For 
exposure inside ships' refrigerators, pork loins, hams, 
sausage, beef, and frozen fish were taken along. There 
were jackets, trousers, parkas, undershirts, drawers, 
socks, boots, helmets, DDT, soap, and even skis. 

Valuable results, impossible to summarize ade- 
quately, were obtained. Combustible materials had a 
tendency to catch fire, presumably due to the thermal 
radiation. This occurred even at distances of one or two 
miles from the Zeropoint. Of course, many of these 
fires could have been brought under control quickly by 
ships' crews, if there had been crews aboard. 

As expected, thermal radiation showed a great pref- 
erence for black surfaces. In many instances black- 
jjainted objects, and even black writing, was burned 
although nearby white surfaces were almost untouched. 
Some objects melted. Rubber objects located near the 
Zeropoint were scorched or burnt. 



Light metal surfaces, such as exteriors of trucks 
and aircraft structures, were frequently demolished. 

Bombs and torpedoes exploded in a number of in- 
stances, but probably not as a direct result of the atomic 
bomb explosion. Secondary causes, such as fires, were 
presumably responsible. 

Army quartermaster stores and other miscellaneous 
equipment exposed showed greater vulnerability, ordi- 
narily, than normal naval deck gear. 


The test animals which had been placed on the 
twenty-two target vessels by Captain Draeger's DSM 
Naval Medical Research Section were removed as soon 
as possible after the detonation. Some of the animals 
were removed on the afternoon of A-Day ; others were 
removed on the two following days. They were brought 
to the BURLESON, where injured animals were given 
good medical care and all animals were examined 

In all, about 35 percent of the animals used in Test 
A had been killed as of late September, 1946. Ten per- 
cent died from air blast, 15 percent from radioactivity, 
and 10 percent were killed for study. 

* Goats are imperturhahle animals. A goat aboard the NI- 
AGARA was photographed hy a close-up automatic motion picture 
camera just as the shock wave struck. The pictures give a clear view 
of the goat, and show him ^nunching his hay without interruption 
as the shock wave struck and debris flew all about. 



Air blast, as expected, was particularly injurious 
to the exposed animals. Principal symptoms of air 
blast injury were contusions and lung hemorrhages. 

Damage to animal's eyes was negligible.* 

Flash burns produced by the thermal radiation did 
considerable damage to animals situated in a direct line- 
of-sight from the detonation. Fur, of course, provided 
important protection. The protection afforded by anti- 
flash creams and clothing was evaluated successfully; 
knowledge is now adequate for giving personnel maxi- 
mum feasible protection against burns. 

Gamma radiation results developed more slowly. 
Animals receiving only slight doses often appeared en- 
tirely normal at first. Later some developed hemor- 
rhagic patches ; a few showed partial loss of hair and 
very few developed testicular atrophy. The more heav- 
ily-exposed animals exhibited hyper-irritability, mus- 
cular weakness, diarrhea, and increased rate of respira- 
tion. Some of these were moribund, with exaggeration 
of symptoms, bloody diarrhea, and inability to stand. 
These symptoms appeared to have caused the animals 
no intense pain. 

Just how does gamma radiation deal its blow '? This 
was one of the questions uppermost in the minds of 
Captain R. H. Draeger and Captain Shields Warren 
as they studied the animals taken off the target ships. 

* This is in accord with experience at Hiroshima and Naga- 
saki, where blindness was caused hy dust and smoke, rather than 
hy the brilliance of the light. 



Their answer was soon forthcoming. By combining 
what had been learned in Japan with the added infor- 
mation garnered at Bikini, a fairly complete under- 
standing w^as arrived at. 

The answer was a triple one: gamma radiation 
reduces the supply of new^ white blood corpuscles, it 
reduces the supply of new red corpuscles, and it reduces 
the supply of materials necessary to prevent excessive 

The most important eifect is the reduction of the 
supply of white blood corpuscles. A very severe dose 
of gamma radiation completely destroys the bone 
marrow's ability to produce white blood corpuscles; 
no new white corpuscles are produced. This would per- 
haps not be serious if the existing white corpuscles 
could last indefinitely. But they do not : in the natural 
course of events most of them disappear in about two 
weeks. Their absence is serious since the body depends 
on them to destroy infections. With no white blood 
corpuscles, the body is easily overpowered by any of 
the common infections threatening from within or 

Red blood corpuscles, too, are a product of bone 
marrow. They too face extinction when a large dose 
of gamma radiation aifects the bone marrow. Exist- 
ing red blood corpuscles may carry on for a month or 
more, but eventually there are few left ; the anemia is 



The third important effect of severe exposure to 
gamma radiation is reduction in the body's ability to 
prevent excessive bleeding. The injured bone marrow 
is no longer able to produce the so-called platelets which 
normally circulate in the blood. Platelets are the 
particles that produce the enzymes essential to blood 
clotting. Without platelets, the supply of the enzyme 
vanishes. Then, when bleeding starts anywhere in the 
body, the blood is unable to form clots ; bleeding con- 
tinues. Hemorrhagic patches may appear almost any- 
where on the body's exterior or interior; such patches 
may appear, for example, on the skin or on mucous 
membranes. Severe hemorrhages may cause death.* 

Useful correlations of injury and distance of the 
animals from the Zeropoint were made. Additional 
correlations were made between injury and intensity 
of effect responsible. This latter correlation was made, 
of course, taking full account of the exact degrees of 
protection afforded the animals. Captain Draeger's 
records show the exact location of each animal; and 
by combining these data with the measured values of 
peak pressure, thermal radiations, and gamma radia- 
tion, very useful analyses result. 

The effect of the gamma-ray dosage given the mice 
will not be known for some time. These animals were 

* Although exposure of the entire tody to a few hundred roent- 
gens may he fatal, exposure of only a small part of the body may 
produce relatively little injury. There is at least one laboratory 
case on record in which a patient's brain was given an X-ray ex- 
posure of 24,000 roentgens, and the patient survived. 



placed so as to receive non-lethal dosage, in order that 
genetic effects, if any, might be followed over several 
generations of progeny. Immediately after the test, 
the mice were flown back to the National Cancer Insti- 
tute. They were bred, and even by late September of 
1946 a few litters had been born. These litters were 
apparently normal; but it was still too soon to tell 
whether cancer would develop.* 

The results obtained on animals and the extensive 
radiation and pressure data obtained form a firm basis 
for estimating the ranges at which exposed and pro- 
tected crew members would be seriously injured; the 
symptoms of injury are far better understood, and ad- 
vances in diagnosis and treatment have been made. 

One general conclusion is that casualties caused 
by the shock wave may be expected to be high for per- 
sons in exposed positions within one half mile of the 
projected Zeropoint. Thermal radiation also may be 
expected to be very harmful to exposed personnel. 
Within the area of extensive blast damage to ship 
superstructures, nuclear radiation may well prove 
fatal ; thin walls of steel cannot insure protection, and 
even thick walls are an imperfect answer. 

* Gamma radiation is prohahly capable of producing chromo- 
some changes which can he transmitted to progeny. It is likely that 
the great majority of such chromosome changes are sufficiently un- 
favorable that no progeny would be born alive; early prenatal 
death would be more likely. Whether or not any mutations with 
power of survival will result from the animals exposed at Bikini 
cannot be decided for some time; such mutations woidd not he 
expected to show up for several generations. 




Test A was over. Sunken ships had been 
marked with buoys. Inspections were complete. A 
few repairs were made to damaged ships ; some wrecked 
equipment was jettisoned. 

Eight Congressmen and thirty-nine press and radio 
representatives returned to the United States. The 
press representatives had radioed 1,000,000 words 
on Test A to their home agencies. The press ship 
APl^ALACHIAN made an interim trip to Pearl Har- 
bor; PANAMINT and BLUE RIDGE made trips to 
Truk, Guam, and other islands; SHANGRI-LA re- 
turned to Roi. 

The wTather was good, and the 42,000 men of the 
Task Force made excellent use of the recreation areas.* 

* The most leavening event of the interval between the tests 
was a practical joke -perpetrated hy two members of the Bureau 
of Ordnance lyistrumentation Group at the expense of their scien- 
tific colleagues. On the evening of A-Day, after the support shijjs 
had re-entered the Lagoon, Dr. C. W. Wyckoff aiid his friends on 
the KENNETH WHITING were leaning against the railing at 
the fantail, staring idly across the dark water. They had got up 
at 4:00 a.m., and they were pretty well exhausted; they were re- 
lieved that the Test had gone off successfully, and that there was 
said to be no dangerous radioactivity about. Suddenly Dr. Wyck- 
off's frieyids pointed to the water beneath them. The water there 



The target fleet was rearranged somewhat. The cen- 
tral ship was to be LSM-60 ; the bomb was to be sus- 
pended some distance beneath her in a watertight steel 
caisson. An especially tall antenna mast had been in- 
stalled to permit line-of-sight transmission of the coded 
radio signal which was to fire the bomb. 

Nearest to the LSM-60, but well over five hundred 
ft. away, were the aircraft carrier SARATOGrA and 
the thirty-four year old battleship ARKANSAS. These 
were both moored broadside to the bomb, to receive the 
maximum impact. Nearby were the concrete oil barge 
YO-160, the submarines PILOTFISH, SKIPJACK, 
and APOGON, and the Japanese battleship NAGrATO. 
In all there w^ere seventy-four target vessels fixed in 
predetermined positions. Roughly forty ships and/or 
small craft were located within one mile of the Zero- 
point, and twenty of these were actually within one 
half mile. 

was distinctly luminous. They watched fascinated, then called more 
colleagues. They exchanged anxious questions as to whether a 
chance accumulation of radioactive materials might he the cause. 
If so, gamma radiation might that very moment he penetrating their 
bodies. They called Dr. J. E. Henderson, who arrived quickly bring- 
ing, on sudden inspiration, a piece of radioactive glass picked up 
months before at Alamogordo, Neiv Mexico. Borrowing a Geiger 
counter, he quickly found that the mysterious glow was harmless 
and certainly a hoax, but he told no one. Instead, he surreptitiously 
placed the radioactive glass near the Geiger counter and allowed 
his colleagues to come to the dread conclusion that the glow was 
indeed highly radioactive. But before the alarm had reached too 
high a pitch, he made a confession, and Dr. Wyckoff reeled in the 
long black string by which his waterproof flashlight had been 



Six of the eight submarines used were placed in 
submerged positions, since it appeared certain that the 
bomb would deliver its greatest punch underwater. 
Placing the submarines in submerged positions some 
distance above the bottom was not easy. The Navy had 
never before had occasion to attempt such a feat. Not 
only must the submarines be fixed at the right depth 
and in normal horizontal position, but the arrangement 
must be secure enough to last for weeks if necessary ; 
and the submarines were to be raised again after the 
explosion. A method of submerging which was found 
satisfactory was to flood certain ballast tanks and then 
attach heavy weights to the submarine 's bow and stern 
by means of long chains of carefully chosen length. The 
weights overcame the submarine's residual positive 
buoyancy and drew her down until the weights them- 
selves rested on the bottom, leaving the submarine at 
the desired depth. The submarine Could be surfaced 
later by pumping air back into the flooded ballast tanks. 
The entire operation was controlled from a salvage 
ship. The illustration Plate XVII shows the submarine 
APOGON in the process of submerging. 

For the underwater explosion, elaborate prepara- 
tions were made for measuring wave heights. Waves of 
unprecedented height were expected, and a unique 
opportunity was j^resented for studying generation and 
propagation of giant waves. 

Preparing the highly-specialized instruments was 
the responsibility of Mr. N. J. Holter, head of the 



Wave Motion Section of the Oceanographic Group.* 
Much reliance was placed on photography. Tower cam- 
eras on Bikini, Amen, and Enyu Islands were synchro- 
nized in a w^ave photography network controlled by 
radio. Cameras on three photographic planes were 
brought into the same network. Each camera was to 
take a photograph every three seconds. 

Television was used also. Two transmitters, operat- 
ing in the 200 megacycle band, were placed in the Bikini 
towers ; ten receivers were used, several of them being 
mounted in PBM planes. 

Many direct-reading wave-height gages were read- 
ied. Thirty of these, called turtles, were laid directly 
on the lagoon bottom. When a wave crest passed, the 
hydrostatic pressure on the bottom increased. Water 
was forced into the instrument through a fine capillary 
tube, a Bourdon-type pressure element was actuated, 
and a small pen drew a significant line on a slowly- 
revolving chart. Use of the capillary tube frequenc}'' 
filter was essential; it prevented the apparatus from 
being wrecked by the extremely intense underwater 
shock wave, which reached the apparatus a few mo- 
ments before the water waves themselves swept past. 
The underwater shock wave came and went within a 

* Lieutenant Commander F. G. Mo7-ris was officer in charge of 
the Wave Measurement Section. Group leaders were Dr. W. K. 
Lyon, Lieutenant C. Sklaw (Navy), Mr. H. W. Iversori, Prof. Alex- 
ander Forbes, and Mr. A. C. Vine. Very important parts in this 
work were played by Dean M. P. O'Brien, Mr. J. D. Isaacs, and 
Lieutenant J. H. Chamblin. 



few thousandths of a second, and failed to penetrate 
the capillary tube appreciably; but the slow-moving 
water wave had no trouble in exerting its effect through 
this tube.* A number of bottom-mounted hydrophones 
(inductiphones) were used also. These, too, measured 
wave height in terms of excess pressure at the bottom 
of the lagoon. 

Some wave-height gages were mounted directly on 
the target vessels. These gages, called portable record- 
ing echo sounders, made continual records of distances 
to the lagoon bottom. Thus as a ship rose and fell on 
a great wave, its changing elevation was recorded. t 
Some echo sounders were mounted on buoys, which rose 
and fell more freely than the cumbersome ships. 

A few of the buoys sent off their wave-height data 
at once, by radio, to scientists in a PBM plane circling 
10 or 15 miles away. 

The last important date before B-Day w^as 19 July 
1946, when the final rehearsal was held. It went 

* These instruments, powered hy batteries, could only operate 
for limited periods and therefore had to he started almost at the 
last moment before the explosion. To make final adjustments on the 
starting mechanisms a number of picked men were kept aboard cer- 
tain of the target ships until a few hours before Mike Hour. These 
men breathed a great deal easier when the small boats showed up 
on schedule to take them out of the lagoon. 

t The echo sounder's main coynponent is a7i imderwaier "trans-' 
ducer," or combination transmitter and receiver of souyid waves 
in water. The transducer gives out a sudden pulse of sound, listens 
for the echo from the bottom, and measures the time interval before 
the echo is received. An increase in time interval corresponds to 
an increase in depth. 



through successfully. However, the weather was dis- 
appointing and much of the aviation program had to 
be cancelled; luckily a complete aviation rehearsal 
had been held separately a few days before. 

The weather prediction for July 25, 1946, which was 
to be B-Day, was indecisive. Colonel B. J. Holzman 
and Captain A. A. Cumberledge (Navy), in charge 
of weather forecasting, studied and restudied the bulle- 
tins being sent in continuall,y from weather reconnais- 
sance planes, land stations, and surface vessels ; by bad 
luck, a so-called tropical front lay almost exactly above 
Bikini Lagoon. But the odds appeared good that the 
front would move oif slowly in favorable manner, and 
at 8 :50 a.m. on July 24, Admiral Blandy made the de- 
cision to get the B-Day program underway. 

Final inspections were made of target vessels, and 
final attentions were given to test animals and scien- 
tific instruments. 

Then the evacuation began. The majority of the 
support ships quit the Lagoon by the evening before 
B-Day. The remainder left by 6 :20 a.m. on the morn- 
ing of B-Day. Among the last persons to leave the 
lagoon was a group consisting of Admiral Parsons, 
Dr. M. Gr. Hollo way, Mr. R. S. Warner, Jr., and a few 
others. This group made the final adjustments aboard 
the bomb-carrying ship LSM-60, and quit her at 6:07 
a.m. Just 148 minutes later, this ship ceased to exist. 

Shortly before How Hour, Dr. M. Gr. Hollo way on 
the CUMBERLAND SOUND periodically closed 



switches which sent to LSM-60 the successive coded sig- 
nals 'preliminary to the actual firing on the bomb. Dr. 
E. W. Titterton counted off the final seconds ; through 
loudspeakers the relentless toll was heard by the 42,000 
men waiting outside the lagoon, and by radio listeners 
throughout the world. 

The bomb detonated at 59.7 seconds after 8 :34 a.m. 
on July 25, 1946, Bikini Local Time. This corresponded 
to roughly 4:35 p.m. on July 24, Eastern Standard 
Time and 9 :35 p.m. on July 24, Greenwich Civil Time. 
The bomb was located at Latitude 11° 35' 05" North, 
and Longitude 165° 30' 30" East. Its position was well 
below the surface of the lagoon. 

Things happened so fast in the next five seconds 
that few e.yewitnesses could afterwards recall the full 
scope and sequence. of the phenomena. B}^ studying 
slow^-motion films and analyzing the records caught by 
the thousands of instruments, the scientists eventually 
pieced together the full story.* 

When the bomb detonated, it released almost ex- 
actly the same amount of energy as had been released 
in Test A, namely 1,000,000,000,000,000,000,000 ergs 
(10-^ ergs), equivalent to a])out 20,000 tons of TNT. 

* Without question one reason ivhy observers had so much 
trouble in retaining a clear impression of the explosion phenomena 
was the lack of appropriate words and concepts. The explosion 
phenoynena abounded in absolutely unprecedented inventions in 
solid geometry. No adequate vocabulary existed for these novel- 
ties. The vocabulary bottleneck continued for months even among 
the scientific groups; finally, after two months of verbal groping, a 
conference was held and over thirty special terms, with carefully 


This energy was transmitted initially as thermal 
radiation, gamma radiation, neutron radiation, other 
nuclear radiations, and shock wave. 

The thermal radiation was extremely intense dur- 
ing the first small fraction of a second; photographs 
taken from the air show the water brightly illuminated 
from beneath the surface. The region in which the light 
originated, called the underwater fireball or "gas 
bubble," rose rapidly to the surface and, still within 
the first small fraction of a second, burst through the 
surface to spearhead the upward shoot of the water 
column. Many observers failed to see any light at all, 
but the photographs taken with the Eastman high- 
speed cameras and the Fastax cameras show clearly 
the presence of a brilliant area atop the column during 
the first instant of its rise. The practical effect of the 
thermal radiation was, of course, almost nil. 

The neutron radiation was of little immediate con- 
sequence. Nearly all of it was absorbed in the sea 
water; almost none reached even the nearest target 
vessels. A significant fraction of the neutrons was ab- 
sorbed by the sodium in the water, thereby producing 
radioactive sodium (Na^''). Neutrons were heavily ab- 
sorbed also by hydrogen, chlorine, and other elements 
found in sea water. 

drawn definitions, were agreed on. Among these terms were the 
following: dome, fillet, side jets, hright tracks, cauliflower cloud, 
fallout, air shock disk, water shock disk, base surge, water mound, 
uprush, after cloud. These terms are defined in later pages of this 



The initial burst of gamma radiation was almost en- 
tirely absorbed in the sea water. But the continuing 
gamma radiation, produced by the fission products was 
of great importance, as we shall see in a later para- 

The shock wave in water was probably the most se- 
vere shock wave ever produced on earth. Water, being 
almost incompressible, forms an almost ideal medium 
for transmitting shock waves. The special miderwater 
gages showed that the pressure very close to the bomb 
must have been far greater than 10,000 pounds per 
square inch. Even at ranges of one-fourth to one-half 
mile the pressure was hundreds or even thousands of 
pounds per square inch. At distances of two to three 
miles the pressure was still intense. 

Throughout most of its course the underwater shock 
wave traveled at the speed of sound, which was roughly 
3500 miles per hour, or about one mile per second. Very 
close to the bomb the velocity was even greater. 

The underwater shock wave spread throughout the 
shallow lagoon as a rapidly expanding circle. Photo- 
graphs taken from the air show this water shock disk 
clearly. But it did not grow entirely uniform; a va- 
riety of irregularities were observed. Coral heads on 
the lagoon bottom in some instances impeded the 
growth and in other instances reflected the shock wave 
towards the surface of the water where it out-cropped 
in peculiar pattern. The shock wave was reflected from 
the underwater portions of the target vessels, and peak 



pressure values measured just behind ships were defi- 
nitely lower than pressures at the near sides of the 
ships. Ordinarily, the pressure values were not as great 
close to the surface of the water as they were at greater 

As the underwater shock wave struck the target 
ships, it delivered terrific blows. A peak pressure of, 
say, 1000 pounds per square inch produces a total force 
of nearly a million tons on the underwater hull of a 
large warship situated broadside. 

The underwater shock wave spread not only out- 
ward but also upward. In fact, it was the upward 
sweep which produced the most unprecedented effect. 
The upward sweep of the shock wave and fireball ' ' gas 
bubble ' ' reached the surface of the lagoon within a few 
hundredths of a second. As the gas bubble approached 
the surface, it produced a swelling called the dome. 
The dome was, of course, illuminated from within ; and 
atop the dome rode the LSM-60. The dome now burst, 
and the fireball and water column leaped upward from 
the lagoon. 

At about this instant, LSM-60 was blown to bits 
and sprayed upward with the column. If the column 
could be called a jet, LSM-60 's departure was about 
the ultimate in jet assisted take-offs. If LSM-60 ever 
sank, it was as a fine rain of steel fragments and dust. 
No large fragment of her was ever found. 

Observers could scarcely follow the lightning ascent 
of the column. Its upward rise was initially at a rate 



greater than a mile per second. Almost at once the 
rate decreased sharply ; the growth was very slow after 
the first five seconds. The altitude reached at the end of 
fifteen seconds was about one mile; at the end of the 
first minute, the altitude was about one and one-half 

The rising mass of water passed rapidly from the 
''hair-do" stage to the crowned funnel stage and finally 
to the full cauliflower stage. Judging from photo- 
graphs taken from drone planes flying directly above, 
the cauliflower appeared to have a relativeh^ hollow 
center. The diameter of the cauliflower sixty seconds 
after Mike Hour was greater than one and one-half 
miles. The diameter of the column or stem itself was 
roughly 2000 ft. 

Rising in the column were various fragments, pre- 
sumably from LSM-60 but possibly from the lagoon 
bottom. Several of the larger fragments left in their- 
wake white condensation trails, called bright tracks. 
A number of the fragments struck the surface of the 
water roughly a mile away. 

Great black blotches appeared in the side of the 
column. One blotch was as large as a battleship. The 
cause of these blotches is not known with certainty. 
One theory is that they consisted of dust and soot 
sucked up from the target vessels. The largest of the 
big dark areas, which appeared near the location of 
the ARKANSAS, may not have been a true blotch at 
all ; perhaps it was a cavernous hole in the side of the 



column. In other words, it may have been a ^'shadow" 
produced in the upward-sweeping water by the rela- 
tively immovable ARKANSAS. 

It is estimated that the column contained several 
million tons of water. Early guesses were that ten 
million tons were tossed up, but later computations 
suggest that two million tons may be a more accurate 
figure. This amount of water would fill a swimming 
pool about twenty feet deep and nearly half a mile in 

But the column was far from being solid water; 
actually it was about 99 percent air. A shell fired from 
a large gun could probably have passed straight 
through the column with little difficulty. Probably the 
water was more or less concentrated in the outer part 
of the column, with the center relatively empty. Some 
scientists believe that if suitable lighting had been 
provided inside the column, a person flying directly 
above could have peered down as far as sea level, and 
possibly even down to the very bottom of the lagoon 

The column wall was not smooth, but was inlaid 
with thousands of separate spikes, or column side jets, 
each as large as a destroyer. As the cauliflower ap- 
proached maturity, these side jets began to fall. More 
and more their points turned downward to form a 
white cascade thousands of feet high. This falling cur- 
tain gathered speed, carrying with it thousands of tons 
of air in the cylindrical plunge back into the lagoon. 




While the column was spurting upward, two kinds 
of shock waves were racing outward. The underwater 
shock wave, described on a preceding page, traveled 
fastest, and did the greatest damage. The shock wave 
in air was less harmful, but was extremely interesting 
in many respects. It had, for example, a dual origin. 
In part it was created by the very rapid expansion of 
the fireball and column in their first instant of escape 
from the water. The shock wave created, shaped like 
an egg standing on end, was so intense that it showed 
up clearly in short-exposure pictures taken from the 
towers on Bikini Island. The concentration of air in 
the shock wave acted like a prism and, by optical re- 
fraction, left a clear elliptical line on the photographic 
films. The shock wave in air was born also from the 
fillet, the circular region surrounding the column base. 
In the fillet area, the water was so violently hammered 
from below that the surface of the lagoon was pushed up 
slightly. The energy within the water could not be con- 
strained to stay there; part of the energy leapt into 
the air to produce an air shock wave proceeding more 
upward than outward. 

The combination of the elliptical shock wave and 
the upward shock wave produced a wave of remarkable 
shape. Where the two effects joined, the shock wave 
had a definite bend, such as occurs where the brim of 
a hat joins the crown. The bend did not last long. As 



the shock wave expanded, it smoothed out the bend 
and in short order assumed nearly hemispherical 

Both the underwater shock wave and the air shock 
wave left their circular marks on the surface of the 
lagoon. The water shock disk expanded very rapidl,y; 
the air shock disk expanded more slowly and showed up 
more clearly in the photographs. 

The shock wave reflection effects were remarkably 
vigorous. Slow-motion pictures show the strange pat- 
terns produced on the surface by the underwater reflec- 
tion of the water shock wave. They show also the typical 
effect produced when the air shock wave struck one of 
the inner ships: the localized reflection created a new 
spherical wave spurting out in many directions. Ac- 
tually, it was not the secondary shock wave itself 
which was photographed, but the secondary conden- 
sation cloud which was pursuing the secondary shock 

The primary condensation cloud Avas tremendous, 
covering an area of roughly six square miles. It had 
started forming within one second of Mike Hour; one 
or two seconds later it had reached the "birthday cake 
on a platter" stage. But it evaporated very rapidly. 
Within eighteen seconds after Mike Hour it had the 
form of a hollow ring, and almost immediately there- 
after it broke up and disappeared. A small conden- 
sation cap formed momentarily directly above the 
cauliflower; it lasted only a few seconds. 




The base surge was an awesome yet deceptive phe- 
nomenon. It looked like a great wave of water. Ac- 
tually it was a rolling mass of flufty spray, mist, and 
air. It was not formed by the explosion proper, but 
as an indirect after-effect. The millions of tons of 
water thundering l)ack into the lagoon created an enor- 
mous volume of spray and mist, which billowed out- 
ward from the column base. The outward velocity of 
this diffuse mass was initially more than fifty miles 
per hour ; later it slowed to twenty-five miles per hour. 
As the base surge spread out, it resembled a steadily 
expanding and fattening doughnut. At first, its height 
was about 300 ft. — a mere three times the height of a 
battleship's mast; later it reached 1000 ft., and ulti- 
mately towered to 2000 ft. 

The base surge, for all its tenuousness, left a kiss 
of death on the majority of the target vessels. The white 
billows carried radioactive fission products equivalent 
to many tons of radium. Gamma radiation issued in all 
directions. The base surge did not merely pass hy the 
ships; its radioactive mist settled on the deck, moist- 
ened every bit of exposed metal, wood, and canvas. 
Even after the moisture evaporated, radioactive resi- 
dues remained. And always the deadly gamma radia- 
tion continued; persons remaining within its reach 
Avould have been doomed. The radius of action is es- 
pecially great downwind, since the surge tends to drift 



in that direction. The base surge is the newest menace 
wrung from within the atomic nucleus. 


Water waves were another type of unleashed fury. 
When the millions of tons of water were ripped from 
the lagoon, an enormous cavity was produced, extend- 
ing probably to the very bottom of the lagoon. Almost 
immediately the surrounding water rushed madly to 
fill the cavity; actually, it over-filled the cavity and 
produced a great mound. The mound then sank slowly 
to the normal level of the lagoon. This rapid dying off 
of the central oscillation in the water probably consti- 
tuted the first experimental verification of the compli- 
cated mathematical theory (Cauchy-Poisson equation). 

From the birth and death of the giant mound, the 
water waves were formed — majestic waves higher 
than had ever before been produced by man and per- 
haps greater than Nature herself ever raised.* No one 
knows how great the waves were near the Zeropoint, 
or whether there actually was inside this cauldron 
anything that could properly be called a wave. But 
near the edge of the column, say 1000 ft. from the 
Zeropoint, the waves were very real. Photographs 
show that the highest wave was eighty to one hundred 
ft. from trough to crest. The wave heights were in 

* Possibly greater- waves were produced when, in 1883, the 
island of Krakatao exploded. 



almost perfect agreement with predictions made before 
the tests. These predictions were based on small scale 
experiments made by the Oceanographic Group at the 
United States Naval Electronics Laboratory, San 
Diego, California, and the Naval Mine Warfare Test 
Station at Solomons Island, Maryland. The explosive 
charges used in those experiments contained TNT and 
weighed from one to 2000 pounds. 

The first wave, the highest of all, contained several 
million tons of water. It traveled with a speed of the 
order of fifty miles per hour, which is just what the 
wave experts had predicted.* 

At the start of its outward travel, the first wave was 
in unstable condition ; its crest tended to get ahead of 
its base. The result was what oceanographers call a 
spilling breaker. But as the wave moved along, its 
height diminished and it lost its tendency to break. 

The first wave soon found itself less high than the 
second wave ; and a little later the third wave claimed 
pre-eminence. This handing down of the honors from 
one wave to the next was in full accord with the expecta- 
tions of the oceanographers, who say that the gf^otip 
velocity is less than the phase velocity. 

* The prediction made hy Commander Roger Revelle and Dean 
M. P. O'Brien was based on the known depth of the lagoon and 
on the rough rule that in shallow water of specified depth all very 
long waves have the same velocity. Knowing the depth, they could 
compute the velocity. In really deep water, of course, the situation 
is entirely different: a wave's velocity depends on its length, long 
waves traveling faster than short ones. 



The waves multiplied as they progressed. Near the 
column there were few of them, but as they approached 
Bikini beach, they were a family of fifteen or twenty. 
Each wave gathered height as it entered the shallow 
water off Bikini, three and a half miles from the Zero- 
point; it drew itself up into a short, steep, plunging 
breaker. Maximum height of the breakers was fifteen 

The uprush was not particularly severe. The water 
rushed up over the beach top, in many areas, and 
caused some flooding and erosion. Thousands of tons 
of beach materials were moved. Several medium-sized 
beach landing craft and small boats were damaged and 
a few huts also. But no noteworthy damage resulted.* 

The ^'backrush" from the first wave swept more 
than 50,000 tons of beach sand into the lagoon. 

The explosion produced much erosion of the lagoon 
floor directly beneath the bomb. The amount of bottom 
material wrenched free was of the order of a million 
cubic yards. The main crater formed was not entirely 

* Maximum water height on Bikini Island was measured hy two 
kinds of height gages: tin-can gages and electrical-fuse gages. The 
tin-can gage consists merely of a tall pole securely mounted ver- 
tically and carrying a number of tin cans at various heights. Each 
can is upright; it is open at the top and has a small awning to keep 
out the rain. If a wave covers the ground to a depth of, say, four 
feet, then all cans helow the four-foot level are filled with water. 
In the electrical-fuse gage, the tin cans are replaced hy wires having 
small gaps. When the water rises enough to immerse a gap, an elec- 
trical current flows and a small electrical fuse is blown out. From. 
inspectio7i of the assembly of fuses, maximum water height can be 
deterynined easily. 



smooth, but was found to contain several secondary 

The majorit.y of the materials torn out settled to 
the bottom within a few hours, forming a thick struc- 
tureless carpet. But thousands of tons of sediment re- 
mained in suspension. Even after two weeks, the water 
still carried a mineral load. Some bottom material had 
been thrown high into the air ; some of it fell onto the 
decks of target vessels. 

A large number of fish were killed in the corner of 
the lagoon where the explosion occurred. Elsewhere in 
the lagoon the fish survived, and outside the atoll the 
fish were practically unaffected either by the explosion 
or the subsequent radiological effects.! 

* The depth of the bottom crater was computed from very ac- 
curate sou7idings made before and after the explosion. The soimd- 
ings were made by members of the Oceanographic Group operating 
from, the hydrographic survey ship BOWDITCH. An ingenious 
but unsuccessfid attempt was made to measure the exact diameter 
of bottom area laid bare by the explosion. Some days before the 
explosion, the Group laid long steel cables on the bottom near the 
Zeropoint, and to these cables they attached a large number of hol- 
low steel cylinders containing unexposed photographic film. It was 
expected that in those areas where the water was swept clear, gamma 
radiation from the underwater fireball would reach the cylinders 
and affect the film. Unfortunately, the explosion was so violent that 
none of the cylinders were ever seen again. 

t Over 40,000 atoll fish were caught. Several new types were 
found. Professional fishermen recruited from the west coast fishing 
industry caught many tons of tuna and other deep sea fish (pelagic 
fish). Unfortunately, 98 percent of these latter were lost when 
YP-636 went aground thirty miles south of San Francisco in Sep- 
tember, 1946. 



A strong earth shock was recorded by seismographs 
located on Amen, eight miles from the Zeropoint. 


The B-Day Bomb sank nine ships and seriously 
damaged many others. 

LSM-60, situated directly above the bomb, disin- 
tegrated instantly. A few of the flying fragments were 
photographed by tower motion picture cameras ; a very 
few fragments fell on other vessels and were later 
picked up by boarding personnel. 

The 26,000 ton battleship ARKANSAS sank almost 
at once, while still obscured by spray and steam. She 
was the closest of the target vessels and was located 
well over 500 feet from the Zeropoint. She suffered 
severe damage to her hull. In sinking, she carried with 
her the dubious honor of being the first battleship to 
be sunk by an atomic bomb, and the first battleship to 
be sunk by a bomb which never touched her. 

The aircraft carrier SARATOGA sank by the stern 
seven and a half hours after Mike Hour. She was the 
next-to-closest of the target ships and was located over 
500 ft. from the Zeropoint. Although she was de- 
signed over 20 years ago and, before she sank, was the 
oldest United States aircraft carrier afioat, she was 
extremely strongly built. In fact her hull had been 
designed originally as that of a battle cruiser, and in- 
cluded . hundreds of watertight compartments. She 
weighed 33,000 tons. By three hours after Mike Hour, 



her stern was clearly low in the water and she had 
begun to list slightly to starboard. By five hours after 
Mike Hour her freeboard had decreased further, and 
observers indulged in some betting as to whether she 
would sink, and when. Admiral Blandy ordered tugs 
to attempt to secure lines to her if practicable and tow 
her to Enyu Island for beaching. But this proved to be 
impossible. The ship herself and the water surround- 
ing her were too "hot" to permit safe approach. She 
sank slowly. Her stern was awash at 3:59 p.m. By 
4 :09 p.m. her deck was completely awash and air could 
be seen blowing from her. The last bit of her super- 
structure sank forever beneath the surface of the la- 
goon at 4:16 p.m. Analysis of photographs of ''Old 
Sara" shows that all moored airplanes and materials 
on her deck had been swept overboard; much of her 
superstructure had been demolished; her distinctive 
stack had crashed to the flight deck and her below-the- 
waterline hull had taken a serious beating. 

The ex- Japanese battleship NAGrATO sank during 
the night, four and a half days after Mike Hour. Only 
a few hours after Mike Hour she took on a list of about 
5 degrees. This list increased so slowly that many ob- 
servers expected her to survive. When her characteris- 
tic silhouette failed to show itself on the morning of 
July 30, surprise was general. No one had seen her 
sink. Undoubtedly openings had been made in her hull. 

Three of the submarines sank. They were the 



these were in submerged position when the explosion 
occurred. Air bubbles and fuel oil escaped from the 
APOGON as she went down. 

YO-160, a concrete oil barge, was seen in photo- 
graphs taken immediately after the explosion, but she 
sank quickly. LCT-1114, a 120-ft. landing craft, cap- 
sized and was later sunk. 

Besides sunken ships, there were many seriously 
damaged ships to bear witness to the power of the 
underwater explosion. Serious damage was done to 
the battleships NEW YORK and NEVADA, the 
cruiser PENSACOLA, the destroyers HUGHES and 
ADE, and LST 133. The HUGHES was soon found to 
be in sinking condition, and the FALLON listed 
badly. Both of these ships were therefore taken in tow 
and beached. 

Damage w^as caused principally by the underwater 
shock wave, which tended to crush ships' hulls and 
seriously jar internal machinery. The pressure wave 
in air w^as severe also, but was responsible ordinarily 
only for less serious damage to superstructures. The 
towering waves of water shared in the production of 
damage. It also tended to move some of the ships 
bodity, outward from the Zeropoint. 


Because the target ships were so radioactive. Cap- 
tain Draeger's men were for several days unable to 


UPPER. Last resting place of the Test B bomb was a sturdy steel caisson 
slung at predetermined depth beneath LSM-60. At exactly 8:35 a.m. 
on July 25, 1946, bomb, caisson, and ship ceased to exist. LOWER. 
A shimmering hemisphere, the condensation cloud, springs into being, 
shrouding the target area. 

Pla+e 25 

This photograph was 
taken by on automatic 
camera mounted in a 
drone plane flying di- 
rectly above the Zero- 
point at the instant of 
detonation, a remarkable 
achievement in drone 
control. The cauliflower 
is funnel-shaped at this 
stage; within its jagged 
rim is a condensation 
cloud nearly a mile in 
diameter, which evapo- 
rated a few seconds later. 

In this oblique view the condensation cloud, still in an early stage, is 
expanding on the heels of the air shock wave at over 700 miles per 
hour. A large ship appears as a tiny black speck in the air shock disk, 
the white area marking the outward sweep of the shock wave across 
the surface of the water. 

Plate 26 


UPPER. The Test B column, containing two million tons of water, rises 
in wroth. It towers above the ex-Japanese battleship NAGATO and 
a large floating drydock. LOWER. Seconds later the great column 
thunders back into the lagoon, unleashing the billowing base surge, 
500-ft.-high wall of spray and mist. 

Plate 27 

This photograph, perhaps the most awesome of all, shows the cauli- 
flower aftercloud looming darkly overhead, the mile-high column now 
fast collapsing, and the base surge plunging towards the NAGATO 
(left) and NEVADA (right). Fission products equivalent to hundreds 
of tons of radium infest the area. 

Plate 28 




\ ^t 


^^*^'****^ :tKk¥^ 

UPPER. Drawing itself up to a height of 15 feet, the first wave pro- 
duced by the underwater explosion pounds Bikini beach. Note the 
height-of-water marker pole. LOWER. Backrush from the waves carried 
50,000 tons of beach sand into the lagoon. Note erosion visible at 
right, and the sand-filled boat. 

Plate 29 

The aircraft carrier SARA- 
TOGA is sinking by the 
stern, seven hours after 
the Test B explosion. She 
was more than 500 feet 
from the Zeropoint, yet 
her below-the- waterline 
hull took a bad beating; 
much of her superstruc- 
ture including her stacks 
had been demolished, 
and all moored airplanes 
and materials on deck 
had been swept over- 

A Navy fireboat washes down the deck of the battleship NEW YORK 
after Test B. This procedure was followed for many of the target ships 
prior to sending inspection parties aboard, since great quantities of 
radioactive water had been thrown onto the decks. A few of the 
ships remained "hot" for months. 

Plate 30 

A number of fish caught after Test B were found to be radioactive. 
By placing them overnight on photographic films, radioautographs 
v/ere obtained, as of the surgeon fish shov/n here. Radioautographs 
v/ere obtained of "hot" algae also. Biological procosce: have, of 
course, no effect on radioactivity. 

The fourteen ships sunk 
in the operation carried 
down with them much 
valuable information, 
such OS instrument rec- 
ords and various types of 
damage to ship struc- 
tures. Divers and under- 
water cameras made 
good a large part of the 
informational gap. Here 
is an underwater photo- 
graph of superstructure 
wreckage, including a 
damaged pressure gage. 

Plate 31 

UPPER. Dr. G. K. 
Green, of the Army 
Ground Group, studies 
a telemetered chart 
mode by on Esterline 
Angus recorder on AG 
LOWER. Composite 
photograph roughly 
comparing the Test B 
cauliflower cloud with 
New York skyscrapers. 
An exact comparison 
would be even more 
extreme. The cauli- 
flower cloud, nearly 
two miles in diameter, 
would overshadow a 
considerable portion 
of Manhattan. It re- 
quires little study to 
appreciate catas- 
trophic destruction. 

Plate 32 


approach the ships on which the test animals were lo- 
cated. Fortunately this situation had been allowed 
for in advance : the animals had been given sufficient 
food and water to last for at least ten days. In fact 
all surviving animals had small supi^lies of food re- 
maining at the time the ships were reboarded. 

The animals were found to have suffered very little 
from shock, and of course, none from heat or light. 

But radioactivity took a heavy toll. Some of the 
animals had died from radioactivity even before the 
ships were reboarded. Many others died later. All the 
pigs died as a result of exposure to nuclear radiations. 
Many rats died from the same cause, but a number were 
still alive in late September, 1946. 

As before, exposure to gamma radiation ])roduced 
a variety of symptoms, including general apathy, weak- 
ness, and tendency to develop secondary infections. 
But it should be remembered that radiation sickness 
is essentiall,y painless ; and in the case of animals, vic- 
tims have no mental anguish such as would presumably 
assail human beings. The animal languishes and either 
recovers or dies a painless death. Suffering among the 
animals as a whole was negligible. By studying them 
we have gained knowledge as to what dangers might 
confront men and what steps would minimize the 

The degree of radioactive poisoning of water and 
ships was impressive. The total amount of radioactive 
materials released was initially equivalent to hundreds 



of tons of radium. Some of the radioactive material 
drifted off in the cauliflower cloud; but much re- 
mained in the lagoon area. The base surge, in its pre- 
cipitant flight outward from the column, carried radio- 
active materials. It drenched the target vessels and left 
them radioactively poisoned. 

Over 90 percent of the target vessel array fell vic- 
tim to radioactivity. The extent of radiological hazard 
went beyond what had been expected. 

Without question, ships' crews would have been 
seriously affected over a wide area. Had the target 
array been manned, casualties and both physical 
and psychological injury would have been very 
great. Rescue and attention to casualties would have 
been difficult and dangerous. "Within 2000 yards of the 
explosion center, ships would probably have been in- 
operative and a lapse of weeks might well have ensued 
before relatively undamaged ships could again have 
been used in combat. 


It was several days before the majority of the target 
vessels could be reboarded. Not until ten days after 
B-Day was it feasible to reboard all the vessels. The 
radioactivity of the ships was more severe than had 
been expected. 

The lagoon itself was re-entered a few hours after 
the explosion. The first boats to approach the target 



array were the unmanned drone boats, controlled by 
radio signals sent from support ships located well out 
of danger. These boats threaded their way through 
the array of ''hot" ships, taking w^ater samples and 
recording just how intense the radioactivity was in 
each area. Manned boats skirted the region cautiously, 
keeping outside of the really ''hot" zones. 

Master charts were prepared on the support ships 
showing danger areas. A "red line" was drawn show- 
ing where the radioactivity exceeded one roentgen per 
day, and was thus unsafe. A "blue line" indicated 
where the activity was less than 0.1 roentgen, and was 
safe. As the lagoon currents slowly spread, shifting 
the contaminated water area, new charts were prepared 
and word sent to all ships.* 

All animals had been taken off the target ships by 
five days after B-Day; some of the scientific instru- 
ments could not be approached with safety for weeks 

* Re-entry of the target area would have been greatly slowed if 
previous studies of lagoon currents had not teen made. Commander 
Roger Revellers Oceanographic Group, besides making model 
studies, had spent weeks finding just where the lagoon currents 
went, and how fast. With dye markers, floating poles, and other 
equipment his group tracked not only the surface currents but also 
the counter -currents flowing along the lagoon bottom. They found 
where the bottom water welled up, and where the surface water de- 
scended. They found how the current changed with wind and 
tide. Thanks to this information, they could assure the Task Force 
Commander that advance scouts would not suddenly find them- 
selves trapped by radioactive water welling up behind them un- 



Decontamination measures were initiated promptly 
by Admiral T. A. Solberg. A number of different 
methods were used in this newest of problems : remov- 
ing radioactive materials from ships' decks, sides, 
superstructures. Streams of water were played on the 
ships; special chemicals were applied; strenuous 
scrubbing was tried. The success of these methods 
varied widely. 

Despite all efforts, radioactive contamination con- 
tinued to be a major problem for many weeks. Some 
of the ships, veritable radioactive stoves, were towed 
to Kwajalein. Some contaminated ships were later 
towed to Pearl Harbor and continental United States 
to permit more convenient study of decontamination 
methods and also to permit training personnel in radio- 
logical safety and decontamination processes.* 

Even some of the support ships found that their 
salt water lines and evaporators became contaminated 

* In late August of 1946, Captain G. M. Lyon, Safety Adviser, 
was requested l)y the Task Force Commander to set up a Radio- 
logical Safety School to train officers in all phases of radiological 
safety. Commander D. L. Kauffman was placed in charge of the 
School. First classes began on Septemher 9, 1946, and the stii- 
dents included roughly 100 officers from Army Air Forces, Army 
Ground Forces, Navy, Marine Corps, and the United States Public 
Health Service. The training program, included a four-weeks aca- 
demic course in Washington, D. C, followed by three months of 
practical instruction in the field. The faculty of the school included 
initially: Lt. Col. A. Roth of the Army Ground Forces, Lt. Col. 
J. M. Talbot, of the Army Air Forces, Comdr. E. G. Williams, of 
the United States Public Health Service, Dr. G. Dessauer of the 
University of Rochester, Dr. R. J. Stephenson of Wooster College, 
and Dr. M. L. Pool of Ohio State University. 



by the radioactive lagoon water. Being well clear of 
the lagoon at the time of the explosion did not prevent 
these ships later feeling the effects of the bomb. 

A number of the support ships, on reaching the west 
coast of the United States, were found to be still af- 
fected by radioactive materials, and were held in tem- 
porary quarantine. Strenuous processes of cleaning 
and decontamination were arranged. Special methods 
of cleaning the sides and bottoms of the ships were 
worked out; oxygen rebreathing apparatus was sup- 
plied to the men doing the work; elaborate checking 
procedures were established. 

Fortunately, no hazard existed to personnel not 
actively engaged in the operation, repair, or cleaning 
of the contaminated portions of the ships. This meant 
that there was no danger to anyone from having these 
ships in harbors and at ordinary docking facilities. 
By observing relatively simple safety precautions, per- 
sonnel working on these ships did so with no danger 
to themselves. 

The homeward voyage of the support vessels from 
Bikini got underway in early August. Few support 
ships remained in the atoll after mid- September. The 
scientists gathered again in their laboratories in con- 
tinental United States, analyzed their instruments' 
records and wrote their detailed reports. Then the 
overall reports were compiled. For the first time the 
full story of what happened at Bikini began to un- 
fold. Now, armed with facts instead of guesses, engi- 



neers and strategists could proceed with their plan- 
ning for a national defense geared to the Nucleonics 

The Joint Task Force was dissolved on November 
1, 1946, by the Joint Chiefs of Staff. Final activities 
were carried on thereafter by a Joint Crossroads Com- 
mittee, of which Rear Admiral W. S. Parsons was 
made Chairman. It is the task of this Committee to 
see that all possible information is gleaned from the 
Operation. Years may elapse before the books may be 
closed and the Operation allowed to settle itself into 
its niche in History. 












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Appendix 2 
List of Principal Participating Officials 

Vice Admiral W. H. P. Blandy, Commander of Joint Task 
Force One, was assisted by a staff including two Deputy Task 
Force Commanders and a Ground Forces Adviser. 

Rear Admiral W. S. Parsons, Deputy Task Force Commander 
for Technical Direction, was assisted by a technical staff includ- 
ing the following: 

Four special assistants : 

Dr. John von Neumann, Scientific Adviser 

Capt. F. L. Ashworth (Navy) Assistant for Aviation 

Capt. Horacio Rivero (Navy) Assistant for Special 

Dr. W. A. Shurcliff, Historian 
Two technical administrators: 

Dr. R. A. Sawyer, Technical Director 
Rear Admiral T. A. Solberg, Director of Ship Material 
Two technical advisers : 

Capt. G. M. Lyon (Navy), Safety Adviser 
Col. S. L. Warren, Radiological Safety Adviser 
Major General W. E. Kepner, Deputy Task Force Commander 
for Aviation, was assisted by Army and Navy officials including 
the following : 

Brig. Gen. T. S. Power, Assistant Deputy Task Force Com- 
mander for Aviation 
Capt. H. D. Riley (Navy), Assistant for Naval Aviation 
Major General A. C. McAuliffe, Ground Forces Adviser, was 
assisted by Col. J. D. Frederick and others. 


Commodore J. A. Snackenberg, Chief of Staff of Joint Task 
Force One, was assisted by four assistant chiefs of staff for person- 
nel, intelligence, operations, and logistics. 

Captain Robert Brodie, Jr. (Navy), Assistant Chief of Staff 
for Personnel, was assisted by Comdr. C. A. Powell, Lt. Comdr. 
H. B. Williams, Lt. M. S. Ochstein (Navy), Lt. (jg) John J. Bab- 
inski (Navy), and Lt. A. J. Meyer (Navy). 

Brigadier General T. J. Betts, Assistant Chief of Staff for 
Intelligence, was assisted by a staff including the following: 


Captain Fitzhugh Lee (Navy), Head of the Public Infor- 
mation Section 

Captain R. S. Quackenbush (Navy), Head of the Non- 
Technical Photography Section 

Colonel H. B. Smith, Head of the Nonparticipating Ob- 
servers Section 

Commander Charles Randall, Head of the Security Section 
Captain C. H. Lyman, Assistant Chief of Staff for Operations, 
was assisted by a staff including the following : 

Capt. W. C. "Winn (Navy), Head of the Ship Operation 

Col. W. D. Ganey, Head of the Air Operation Section 

Capt. K. M. Gentry (Navy), Head of the Communications 
and Electronics Section 

Col. B. J. Holzman, Head of the Aerology Section (Working 
closely with him was Capt. A. A. Cumberledge (Navy) ) 

Capt. A. B. Leggett (Navy), Head of the History and 
Analytical Section 
Brigadier General D. H. Blakelock, Assistant Chief of Staff 
for Logistics, was assisted by a staff including the following: 

Capt. M. A. Norcross (Navy), Head of the Executive 

Comdr. M. H. Gatchell, Head of the Navy Supplies Section 

Col. F. W. Ott, Head of the Army Supplies Section 

Col. A. D. Higgins, Head of the Transportation Section 

Comdr. J. J. Fee, Head of the Force Maintenance Section 

Capt. W. E. Walsh (Navy), Head of the Force Medical 

Comdr. K. C. Lovell, Head of the Construction Section 


Dr. R. A. Sawyer, Technical Director, was assisted by a large 
technical staff including six immediate assistants, and ten adminis- 
trators. The six immediate assistants were : 

Dr. E. W. Thatcher, Deputy Technical Director 

Capt. F. L. Riddle (Navy) 

Comdr. E. S. Gilfillan 

Comdr. A. W. McReynolds 

Lt. Comdr. J. K. Debenham 

Lt. (jg) J. A. Young 

Ens. H. M. Archer 


The ten administrators were as follows : 

Dr. W. 6. Penney, head of the Pressure Group (Cans and 

Comdr. Roger Revelle, Head of the Oeeanographic Group. As- 
sisting him in the direction of the oeeanographic survey work were 
Lt. Comdr. C. A. Barnes and also Lt. Comdr. J. R. Lyman, Lt. 
Comdr. M. C. Sargent, Capt. M. A. Traylor (Army), assisting in 
the direction of wave measurement work were Lt. Comdr. F. G. 
Morris and also Mr. N. J. Holter, Comdr. Beauregard Perkins, Jr. 

Comdr. C. H. Gerlach, head of the BuShips Instrumentation 
Group. Principal assistants were Comdr. R. M. Langer, Lt. Comdr. 
L. S. Beedle, Lt. Comdr. F. J. Dellamano and also Mr. E. E. John- 
son, Dr. G. E. Hudson, Dr. Irwin Vigness, Mr. P. J. Walsh, Mr. 
H. E. Jensen, Mr. C. F. Kasanda, Mr. F. J Friel. 

Capt. C. L. Engelman (Navy), head of the Electronics Grouj). 
Principal assistants were Dr. T. D. Hanscome, Comdr. J. L. Miller, 
Comdr. J. E. Rice, Comdr. J. G. Houpis, Dr. D. G. Fink, Comdr. 
F. X. Foster, Lt. Comdr. R. L. Reaser, Lt. Lawrence Bershad 

Col. S. L. Warren, head of the Radioactivity Group. Principal 
assistants were Col. A. A. deLorimier, Capt. R. J. Buettner (Navy), 
Comdr. D. L. Kauffman, Dr. Herbert Scoville, Jr., Dr. Joseph 
Hamilton, Dr. Kenneth Scott, Dr. Gerhard Dessauer, Dr. Lauren 
Donaldson, Mr. Donald Collins. 

Capt. A. E. Uehlinger (Navy), head of the BuOrd Instrumenta- 
tion Group. Assisting him were Dr. G. K. Hartmann, Capt. L. W. 
McKeehan (Navy), Lt. Comdr. F. L. Yeo, Dr. C. W. Lampson, Dr. 
A. B. Arons, Dr. J. V. Atanasoff, Comdr. S. S. Ballard, Dr. J. E. 
Henderson, CWO J. P. Orr. 

Dr. M. G. Holloway, head of the Los Alamos Group. Assisting 
him were Mr. R. S. Warner, Jr., Dr. N. N. Nereson, Dr. G. A. 
Linenberger, Dr. William Rubinson, Dr. J. L. Tuck, Dr. B. Brixner, 
Dr. J. Wieboldt, Dr. J. Wiesner, Dr. H. Weiss, Dr. J. Hirshfelder. 

Comdr. George Vaux, head of the Remote Measurements Group. 

Capt. R. S. Quackenbush (Navy), head of the Technical Photo- 
graph Group. Principal assistants were Comdr. J. H. McElroy, 
Col. P. T. Cullen, Comdr. K. S. Shaftan, Dr. Brian O'Brien, Lt. 
F. Terzo (Navy), Dr. B. Brixner. 

Col. D. F. Henry, head of the AAF Electronics Group. 



Rear Admiral T. A. Solberg, Director of Ship Material, was 
assisted by a large staff including six special assistants and six 
group administrators. His six principal special assistants were as 
follows : 

Capt. L. A. Kniskern (Navy) 
Capt. F. W. Slaven (Navy) 
Capt. F. X. Forest (Navy) 
Comdr. E. H. Batcheller 
Lt. Comdr. L. H. Roddis, Jr. 
Lt. Comdr. L. R. Crlostcn 

His six group administrators were as follows : 

Col. J. D. Frederick, head of the DSM Army Group. Principal 
assistants were Col. J. S. Weber, Lt. Col. S. B. Smith, Capt. C. H. 
Wollenberg (Army), Lt. Col. S. F. Musselman, Capt. H. C. Adams 
(Army), Col. L. P. Jordan, Maj. E. K. Walters. 

Capt. T. C. Lonnquest (Navy), head of the DSM Aeronautics 
Group. Principal assistants were Capt. J. E. Dodson (Navy), 
Comdr. J. K. Leydon, Maj. J. W. Morrison, Comdr. J. R. Reedy, 
Lt. E. V. Sizer (Navy), Lt. Comdr. G. V. Schliestett, Lt. Comdr. 
W. A. Hopkins, Lt. J. A. Torrey (Navy). 

Capt. L. A. Kniskern (Navy) was originally head of the DSIM 
BuShips Group; later Capt. F. X. Forest (Navy) was made head 
of the Group. Principal assistants were Capt. F. W. Slaven (Navv), 
Capt. R. C. Bell (Navy), Comdr. C. L. Gaasterland, Lt. (jg) J.'F. 
DiStefano, Comdr. J. W. Roe, Capt. W. S. Maxwell (Navy), Capt. 
P. S. Creasor (Navy). 

Capt. E. B. Mott (Navy) was head of the DSM Ordnance Group. 
Principal assistants were Comdr. A. A. Freedman, Capt. C. S. 
Piggott (Navy), Comdr. Edgar O'Neill, Comdr. F. W. Russe, 
Comdr. H. C. Dudley, Lt. Comdr. H. B. Taylor, Lt. Comdr. H. M. 
Tatum, Lt. Comdr. T. W. Johnson 

Capt. G. M. Lyon (Navy) was head of the DSM Medical Group. 
Principal assistants were Capt. Oscar Schneider (Navy), Comdr. 
Marshall Cohen, Lt. Harry Browdy (Navy), Lt. (jg) A. L. Rogers, 
Lt. G. W. Morrison, Jr. (Navy), Lt. Comdr. J. J. McCoy; also Capt. 
R. H. Draeger (Navy), Capt. Shields Warren (Navy), Comdr. R. H. 
Lee, Comdr. J. L. Tullis, Lt. Comdr. R. E. Smith, Lt. Maynard 
Eicher (Navy), Capt. F. R. Lang (Navy), CPhM C. E. Wagner. 

Capt. C. L. Engelman, head of the DSM Electronics Group. 
(See also electronics personnel listed under Technical Director's 



The eight task group commanders were as follows : 
E. Adm. W. S. Parsons, Technical Group, T.Gr. 1.1 
R. Adm. F. G. Fahrion, Target Vessel Group, T.G. 1.2 
Capt. W. P. Davis (Navy), Transport Group, T.G. 1.3 
Col. J. D. Frederick, Army Ground Group, T.G. 1.4 
Brig. Gen. R. M. Ramey, Army Air Group, T.G. 1.5 
R. Adm. C. A. F. Sprague, Navy Air Group, T.G. 1.6 
Capt. E. N. Parker (Navy), Surface Patrol Group, T.G. 1.7 
Capt. G. H. Lyttle (Navy), Service Group, T.G. 1.8 


Principal Rear Echelon officials included: 

Rear Adm. F. J. Lowrey, Commander of Rear Echelon 

Capt. H. R. Carson (Navy), Chief of Staff 

Col. G. W. Trichel, Ground Force Adviser 

Col. R. C. Wilson, Commander for Aviation 

Comdr. D. Klein, Commander for Technical Direction 

Lt. Comdr. D. M. Rubel, Asst. Chief of Staff for Personnel 

Comdr. K. Daly, Asst. Chief of Staff for Intelligence 

Lt. Comdr. P. J. Kidding, Asst. Chief of Staff for Operation 

Maj. W. H. Lollar, Asst. Chief of Staff for Logistics 

Appendix 3 

Joint Crossroads Committee 

The Joint Crossroads Committee was created by the Joint Chiefs 
of Staff on November 1, 1946, to succeed Joint Task Force One, 
which went out of existence on that day. 

The membership of the Committee was as follows : 
Rear Admiral W. S. Parsons, Chairman 
Brigadier General T. S. Power, Army Air Forces Member 
Colonel C. H. M. Roberts, Army Ground Forces Member 
Rear Admiral T. A. Solberg, Navy Member 
Captain H. R. Carson (Navy), Executive Secretary 
Supporting officials were as follows: 

Captain F. L. Ashworth (Navy), Technical Assistant 

Captain A. J. Bibee (Marine Corps), Photographic Files 

Dr. E. S. Gilfillan, Technical Director 

Major J. B. Gulley, Security 

Commander D. L. Kauffman, Radiological Safety Instruction 

Captain G. M. Lyon (Navy), Safety Consultant 

Captain L. A. O'Brien (Army), Army Personnel 

Captain Horacio Rivero (Navy), Technical Assistant 

Lieutenant Commander J. D. Roche, Documentary Film 

Dr. H. P. Scoville, Jr., Radiological Safety Reports 

Dr. W. A. Shurcliff, Historian 

Captain F. I. Winant, Jr. (Navy), Technical Assistant 

Captain G. E. Zawasky (Marine Corps), Communications 


Appendix 4 

The Evaluation Board 

The Evaluation Board was created by the Joint Chiefs of Staff, 
its functions were (1) to be available for advising the Commander 
oL' Joint Task Force One in his planning of the tests, and (2) to 
prepare and present to the Joint Chiefs of Staff an evaluation of 
tlie results of the tests. 

The complete membership of the Board, as announced on March 
28, 1946. was as follows: 

Dr. K. T. Compton, President of the Massachusetts Institute 

of Technology (Chairman) 
Mr. Bradley Dewey, President of the American Chemic:;! 

Society (Vice Chairman) 
Mr. T. F. Farrell, New York State Department of Public 
Works, formerly Major General in the Manhattan Engi- 
neer District 
General J. W. Stilwell. Commanding General, Sixth Army 

Lieutenant General L. H. Brereton, on Special Duty in the 

Office of the Secretary of War 
Vice Admiral J. H. Hoover, a member of the Navy General 

Rear Admiral R. A. Ofstie, Senior Navy Member of the 
U. S. Strategic Bombing Survey 
After General Stilwell's death, Lt. General A. C. Wedemeyer, 
Commanding General of the 2nd Army, was made a succeeding 

The Board made careful study of the Operation Plan, and 
witnessed both tests. It observed Test A from an airplane located 
twenty miles from the Zeropoint. Four members witnessed Test B 
from an airplane eight miles from the Zeropoint, while the other 
three members w^ere stationed on the hospital ship HAVEN, eleven 
miles from the Zeropoint. Detailed inspections were made of the 
target ships, and the technical reports were carefully studied. 

The Board's final report, not yet completed, is expected to 
include conclusions on strategic, tactical, and technical matters 
pertinent to national defense. Preliminary reports, issued immed- 
iatelv after each test, are presented in this volume as Appendices 
10 aiid 11. 


Appendix 5 

The President's Evaluation Commission 

An Evaluation Commission was created by the President and 
given the function of (1) cooperating with the Secretaries of War 
and Navy in the conduct of the Tests, and (2) undertaking a study 
of the tests and submitting to the President a report of its obser- 
vations, findings, conclusions, and recommendations. 

The finally established membership, announced on March 30, 
1946, Avas as follows : 

Senator C. A. Hatch, New Mexico (Chairman) 
Senator Leverett Saltonstall, Massachusetts 
Representative W. C. Andrews, New York 
Representative Chet Holifield, California 
. Dr. K. T. Compton, President of the Massachusetts 
Institute of Technology 
Dr. E. U. Condon, Director of the National Bureau 

of Standards 
Mr. Bradley Dewey, President of the American Chemical 

Mr. W. S. Newell, President of the Bath Iron Works 

Mr. Fred Searls, Jr., special assistant to the Secretary 
of State 
Members witnessed the tests from airplanes and surface vessels. 
Brief reports, included here as Appendices 12 and 13, were 
made after each test. 


Appendix 6 

United Nations Observers 

Each country having membership in the United Nations Atomic 
Energy Commission was invited to choose two observers. The ob- 
servers actually attending were as follows : 

Brazil : 

Canada : 
China : 

France : 

Egypt : 

Commander S. H. K. Spurgeon, R.A.N. 

Major Orlando Rangel (Army) 
Captain Alvaro Alberto de Motta y Silva 


Air Vice Marshal E. W. Stedman 
Major General R. M. Luton (Retired) 

Chung- Yao Chao, Director of the Department 
of Physics, National Central University 

Major General Fisher Hou, Military Attache, 
Washington, D. C. 

Captain de Fregate Pierre Balande, General 

Staff (Navy) 
Mr. Bertrand Goldsehmidt 

Colonel Hassen Ragab, Military Attache, 

Washington, D. C. 
Lieutenant Colonel Abdel-Gaffar Osman, Chief 
Inspector of Explosives (Army) 
Great Britain: Flight Lieutenant F. Beswick, M.P., R.A.F. 

Commander A. H. P. Noble, M.P., R.N. 
Mexico : Mr. Juan Loyo Gonzalez 

Dr. Nabor Carillo 
Netherlands : Captain G. B. Salm, Head of Naval Intelligence 

Major H. Bruining, Ministry of Supply 
Poland : Mr. Stefan Pienkowski, President, University 

of Warsaw 
Mr. Anrzej Soltan, Head of Physics Depart- 
ment, University of Lodz 
U.S.S.R. : Dr. A. M. Mescheryakov, Head, Physics Depart- 

ment, University of Leningrad 
Mr. S. P. Alexandrov 


Appendix 7 

Congressional Observers 

Immediately following the June 14, 1946, passage by Congress 
of House Joint Resolution 307 authorizing use of 33 United States 
combatant vessels as target vessels, invitations were extended to a 
number of Congressmen to witness the tests. 

Thirteen Congressmen witnessed Test A and seven witnessed 
Test B. They were as follows: 

Cordon, Guy, Oregon 
Hatch, C. A., New Mexico 
Hickenlooper, B. B., Iowa 
Saltonstall, Leverett, Massachusetts 

Anderson, J. Z., California 
Andrews, W. G., New York 
Bates, G. J., 'Massachusetts 
Bradley, M. J., Pennsylvania 
Engel, A. J., Michigan 
Gillespie, Dean M., Colorado 
Holifield, Chet, California 
Izac, E. v., California • 
Norrell, W. F., Arkansas 
Rooney, J. -T., New York 


Appendix 8 

Support Vessels 


Commanding Officer 

(a) Force Flagship (carrying Vice Admiral 

W. H. P. Blaiidy, Task Force Commander) 

MT. Mckinley (agc-7) 

Capt. W. N. Gamet 

(b) Target Vessel Control Group (part of Task 
Group 1.2, commanded by Rear Admiral F. G. 

FALL RIVER (flagship) (CA-131) 

Capt. D. S. Crawford 

(c) Technical Group (Task Group 1.1, commanded 
by Rear Admiral W. S. Parsons) 







HAVEN (APH-112) 

BEGOR (APD-127) 



Capt. E. H. Echelmeyer, Jr. 
Capt. A. R. Truslow, Jr. 
Capt. H. R. Horney 
Capt. V. F. Gordinier 
Comdr. D. E. Pugli 
Capt. C. L. Carpenter 
Capt. A. C. Thorington 
Lt. Comdr. R. K. Margetts 

Cjmdr. H. A. Owens 

(■d) Transport Group (Task Group 1.3, commanded 
by Captain W. P. Davis (Navy)) 

BEXAR (APA-237) 

Capt. M. M. Bradley 
Capt. J. C. Landstreet 
Capt. J. B. Williams 
Capt. H. W. Howe 
Capt. W. H. Truesdell 
Capt. G. P. Enright 
Capt. C. H. Walker 
Capt. C. E. Carroll 
Capt. H. B. Edgar 
Capt. C. C. Ray 
Comdr. M. E. "Selby 
Capt. M. Durski 
Comdr. A. K. Ehle 
Capt. J. B. Renn 
Capt. C. R. Criddle 
Capt. W. B. Ammon 
Lt. (jg) J .A. Scott 
Lt. (jg) J. M, Scott 





DD-692 A. M. SUMNER 









(g) Service Gr 
by Captain 

DIXIE (AD-14) 



SEVERN (A0-(W)-61) 





AJAX (AR-6) 
















Commanding Officer 

(e) Navy Air Group (Task Group 1.6, commanded 
by Rear Admiral C. A. F. Sprague) 

Capt. W. D. Cogswell 
Capt. T. U. Sissons 
Comdr. J. D. Sliea 
Comdr. E. B. Rittenhouse 
Comdr. W. Outerson 
Comdr. C. J. Heath 
Comdr. N. E. Smith 

(f) Surface Patrol Group (Task Group 1.7, com- 
manded by Captain E. N. Parker (Navy) ) 

Lt. Comdr. W. R. Laird 
Comdr. J. W. Howard 
Comdr. R. P. Walker 
Comdr. F. A. Brock 
Comdr, H. P. Mclntire 
Comdr. T. F. McGillis 
Comdr. O. D. Waters, Jr. 
Comdr. H. E. Day 
Comdr. E. S. Miller 

Comdr. M. Thompson 

oup (Task Group 1.8, commanded 
G. H. Lyttle (Navy)) 

Capt. J. C. Goodnough 

Comdr. A. C. Harshman 

Capt. W\ M. Searles 

Capt. M. H. McCoy 

Comdr. W. C. Cross 

Lt. J. R. Davidson 

Comdr. D. A. Crandall 

Comdr. H. B. MacLeod 

Capt. J. R. Clark 

Lt. W. F. Horstkamp 

Lt. F. B. Schwenneker 

Comdr. D. B. Candler 

Lt. Comdr. H. T. Smith 

Lt. (jg) H. G. Salisburv 

Capt. A. R. St. Angelo 

Lt. W. H. Moore 

Lt. Comdr. F. C. Ziesenhenne 

Ens. J. H. Richter 

Lt. J. B. Warner 

Lt. (jg) F. H. La Pierre 

Lt. E. B. Terrio 

Lt. (jg) P. H. Sullivan 

Lt. J. T. Gordon 



QUARTZ (IX-150) 

Commanding Officer 


ETLAH (AN-79) 



Lt. J. Buday 
Lt. T. P. Pierce 
Comdr. R. N. Newton 
Lt. (jg) R. K. Ritzett 

Salvage Unit (Task Unit 1.2.7, commanded by 
Captain B. E. Manseau (Navy)) 

Lt. Comdr. R. H. Drazell 

Lt. C. B. Hiner 

Lt. H. F. Gindling 

Lt. F. F. Sharp 

Lt. Comdr. S. D. Frey 

Lt. Comdr. C. H. Rooklidge 

Lt. J. S. Lees 

Lt. Comdr. F. H. Matthews 

Lt. C. H. McCuUar 

Lt. A. F. Hamby 

Lt. J. E. Reid 

Lt. Comdr. C. S. Horner 

Lt. Comdr. A. V. Swarthout 

Lt. L. E. Marsh 

Lt. L. G. Hickle 

Lt. (jg) J. B. Birtch 

Lt. (jg) M. F. Root 

Lt. E. R. Weaver 

Lt. R. B. Leonnig 

Lt. (jg) A. Morris 

Lt. A. J. Roberts 

Lt. R. E. Ward 

Despatch Boat and Boat Pool Unit (Task Unit 
1.8.3, commanded by Comdr. J. G. Blanche) 
Comdr. J. G. Blanche 
Lt. Comdr. W. H. Barchmann 
























Commanding Officer 

Lt. B. F. Caver 
Lt. (jg) E. A. Clark 
Lt. (jg) J. W. Ferrill 
Lt. (jg) J. T. Moss 
Lt. (jg) N. C. Thomas 
Lt. (jg) J. L. DeBlock 
Lt. (jg) G. A. Oberle 
Lt. (jg) H. P. Cohn 
Ens. H. W. Phipps 
Ens. E. R. Nutter 
Lt. L. r. Koch 
Lt. L. F. Koch 
Lt. (jg) J. D. Simmons 

Lt. (jg) P. M. Mitchell 
Ens. J. T. Jans 


(j) Medical Unit (Task Unit 1.8.4, commanded by 
Captain E. P. Creehan (Navy)) 

Capt. D. M. Maekey 
Capt. E. P. Creehan 

(k) Survey Unit (Task Unit 1.8.5, commanded by 
Captain C. B. Schiano (Navy)) 









Capt. C. B. Schiano 
Lt. F. A. Wodke 
Lt. E. E. Simms 
Lt. C. D. Bailey 
Ens. E. J. Litty 
Ens. C. M. Clancy 
Ens. V. P. Finos 
Ens. R. H. Zisette 


(1) Evacuation Unit (Task Unit 1.8.7, commanded 
by Lieutenant G. H. Gromer (Navy)) 

Ens. M. B. Fletcher 
Lt. G. 11. Gromer 


Appendix 9 

Target Vessels, Test A 

(Note: all target vessels were under the general com- 
mand of Rear Admiral F. G. Fahrion, commander of 
Task Group 1.2) 

Ship Commanding Officer 

(a) Battleships and Cruisers (Task Unit 1.2. 
commanded by Captain W. Deweese) 

ARKANSAS, Br.:];! 
NAGATO, Japanese BB 
SAKAWA, Japanese CL 

Capt. W. Deweese 
Capt. L. H. Bibby 
Capt. C. C. Aden 
Capt. C. H. Bushnell 
Capt. D. J. Ramsey 
Capt. J. Conner 
Capt. W. J. Whipple 
CaiJt. H. L. Stone 
Capt. A. II. Graubart 

(b) Aircraft Carriers (Task Unit 1.2.2, commande( 
by Captain N. M. Kindell) 


Capt. O. S. MacMahan 
Capt. N. M. Kindell 

(c) Destroyers (Task Unit 1.2.3, 
Comdr. L. W. Sedgwick) 

commanded ])v 

EHIND, DD-404 
STACK, DD-406 

TUNA, SS-203 
SKATE, SS-305 

Lt. Comdr. H. H. Ellison 
Lt. Comdr. F. W. Bampton 
Comdr. M. Harvev 
Lt. Comdr. B. W.'Spore 
Comdr. M. H. Buaas 
Lt. Comdr. D. M. Sharer 
Comdr. E. A. Shuman 
Lt. Comdr. R. H. Pauli 
Comdr. D. S. Bill, Jr. 
Lt. Comdr. J. J. McMullen 
Lt. Comdr. J. C. Mathews 
Comdr. L. W. Sedgwick 

(d) Submarines (Task Unit 1.2.4, commanded bv 
Comdr. R. A. Waugh) 

Lt. Comdr. F. J. Coulter 

Lt. Comdr. R. C. Smallwood, J i-. 

Lt. Comdr. G. Jacobsen 

Lt. Comdr. E. P. Huey 

Lt. Comdr. J. W. Johnson 




EST 52 
EST 220 
EST 545 
EST 661 
ECI 327 
ECI 329 
ECI 332 
ECI 549 
ECT 745 
ECT 816 
ECT 818 
ECT 874 
ECT 1013 
ECT 1078 
ECT 1112 
ECT 1113 
ECM 1 



Commanding Officer 

Comdr. R. A. Waugh 
Lt. Comdr. H. G. Reaves 
Et. Comdr. R. B. Eaning 

(e) Landing Craft (Task Unit 1.2.5) 

Et. (jg) C. E. Boggs 
Et. (jg) J. O. Marzluff 
Et. (jg) S. E. Voiler 
Et. W. F. Marlow 
Ens. R. P. Eemke 
Ens. R. C. Hayes 
Ens. W. F. Zartman 
Et. (jg) W. F. Fergusen 

(f) Merchant-Type Ships (Task Unit 1.2.6, com- 
manded by Capt. W. H. Standley, Jr.) 

Capt. D. F. Williamson 
Comdr. W. E. Kitch 
Comdr. J. E. Kendall 
Capt. E. S. Mewhinney 
Comdr. C. S. Eee 
Capt. W^. S. Rodimon 
Et. Comdr. A. B. Taylor 
Capt. A. R. Montgomery 
Comdr. E. T. Goyette 
Et. Com. J. E. Hunter 
Capt. E. B. Ellis 
Comdr. J. E. Haines 
Capt. P. C. Crosley 
Capt. D. D. Humphreys 
Comdr. W. W. Sackett 
Capt. E. E. Divoll 
Capt. A. S. Carter 
Capt. P. J. Neimo 
Capt. W. H. Standley, Jr. 

(g) Concrete Drydocks and Barges 


Appendix 10 

Preliminary Statement by the Evaluation Board 

Test A 

The following preliminary statement on Test A was prepared 
by the Joint Chiefs of Staff's Evaluation Board immediately fol- 
lowing Test A. The statement was released by the White House 
on July 11, 1946. 

The members of the Board inspected target ships the day before 
the test, witnessed the explosion from an airplane twenty miles dis- 
tant, and then approached to within nine miles for a brief view. 
On the following day, as soon as safety clearance had been received, 
the members flew to Bikini and began their examination of ship 
damage. Many photographs had been studied, and military and 
scientific specialists interviewed in an attempt to obtain an over-all 
understanding of test results prior to the compilation of all the 

From its previous study of the plans for the test, and from its 
observations in the Bikini Area, the Board considers that the test 
was well conceived and well executed by the services in close co- 
operation with a large civilian staff. It is satisfied in that the con- 
ditions of the test were well-chosen and that the highest skill and 
ingenuity have been used to obtain a maximum amount of data 
in an unbiased, scientific manner. It believes that the commander, 
staff, and personnel of Task Force One deserve high commendation 
for their excellent performance and their notable cooperative spirit. 

Effective precautions appear to have been taken to safeguard 
personnel against radioactivity and associated dangers. 

The Board's present information is that the bomb exploded with 
an intensity which approached the best of the three previous bombs, 
over a point 1500 to 2000 feet westerly of the assigned target, and 
at approximately the planned altitude. 

The target array in no sense represented an actual naval dis- 
position but was designed to obtain the maximum data from a single 
explosion. The most important eff'ects produced by the bomb are 
the following: 

a. A destroyer and two transports sank prom])t]y and another 
destroyer capsized. It later sank, and the Japanese cruiser 


SAKAWA sank the following day. The superstructure of the sub- 
marine SKATE was so badly damaged as to make it unsafe to 
submerge the vessel. The light carrier INDEPENDENCE was 
badly wrecked by the explosion, gutted by fire, and further dam- 
aged" by internal explosions of low order, including those of tor- 
pedoes. All the above vessels were within one-half mile of the 
explosion point. 

J). Numerous fires were started on other ships, including one 
on a ship two miles distant, which was apparently due to some 
unusual circumstance since the other fires were much closer. Here 
it should be remembered that the target ship decks carried a great 
variety of test material not ordinarily exposed on the decks of naval 

c. The only major combatant ships within one-half mile of the 
explosion point were the battleships NEVADA and ARKANSAS 
and the heavy cruiser PENSACOLA. The blast struck these from 
the after quarter. Apparently little damage was done to their hulls 
or their main turrets but their superstructures were badly wrecked. 
These ships were unquestionably put out of action and would, along 
with many others within three-fourths of a mile, have required 
extensive repairs at a principal naval base. 

d. Other ships on the target array suffered damage in varying 
degree, depending on position and type of ship, but there was 
relatively little damage at distances greater than three-fourths of 
a mile. 

e. The primary material effects noted were due to blast, buck- 
ling of decks and bulkheads, and destruction or deformation of 
lightly constructed exposed objects, including stacks, masts, and 
antennae. Secondary effects were due to fire, and it is noteworthy 
that Army Quartermaster stores and miscellaneous equipment 
placed on the decks for the test proved more vulnerable than nor- 
mal naval deck gear. It should be pointed out that since the targets 
carried no personnel the fires were uncontrolled and undoubtedly 
there was more damage than there would have been under battle 
conditions. Singularly, although considerable amounts of explosive 
ordnance were exposed on decks and in gun turrets, there is no 
indication on ships which remained afloat that any of this ma- 
terial was exploded by direct action of the atomic bomb. Fire- 
fighting ships entered the target area as soon as they could obtain 
radiological security permission and subdued a number of fires. 
The speed and efficiency with which these ships acted preserved for 
later examination a great deal of evidence of bomb action which 
might otherwise have been lost. 


/. Examination of the flashburn effects produced by the initial 
radiation from the explosion indicates that casualties would have 
been high among exposed personnel. However, it is the opinion 
of the Board that persons sheltered within the hull of a ship or 
even on deck in the shadow of radiation from the bomb would not 
have been immediately incapacitated by burns alone, whatever have 
been the subsequent radiological effects. 

g. Within the area of extensive blast damage to ship super- 
structures there is evidence that personnel within the ships would 
have been exposed to a lethal dosage of radiological effects. 

Personnel casualties due to blast would no doubt have been 
high for those in exposed positions on vessels within one-half 
mile of the target center. Beyond this, any discussion of the blast 
effect upon personnel will have to await the detailed reports of the 
medical specialists. 

In general no significant unexpected phenomena occurred, 
although the test was designed to cope with considerable variation 
from predictions. There was no large water wave formed. The radio- 
active residue dissipated in the manner expected. No damage oc- 
curred on Bikini Island, about three miles from the explosion 

From what it has seen and from what it has ascertained from 
data now available, the Board is able to make certain general 
observations : 

a. The atomic bomb dropped at Bikini damaged more ships 
than have ever before been damaged by a single explosion. 

5. The test has provided adequate data of a sort necessary 
for the redesign of naval vessels to minimize damage to superstruc- 
tures and deck personnel from this type of bomb. Because of the 
nature of the first test (air blast) little information has been ob- 
tained on hull effects. Damage to ships' hulls will be studied spe- 
cifically in the second test when a bomb will be exploded under 

c. A vast amount of data which will prove invaluable through- 
out scientific and engineering fields has been made available by this 
test. Once more the importance of large-scale research has been 
dramatically demonstrated. There can be no question that the effort 
and expense involved in this test has been amply justified both by 
the information secured and by greatly narrowing the range of 
speculation and argument. Moreover, it is clear to the Board that 
only by further large-scale research and development can tlie 
United States retain its present position of scientific leadership. 
This must be done in the interests of national safety. 


The board desires to say that it has had the fullest cooperation 
of the task force commander, and that every opportunity has been 
afforded it in carrying out its mission. The members of the Board 
have had access to all data thus far accumulated and have had 
every facility for personally inspecting the results of the test. 

Appendix 1 1 

Preliminary Statement by the Evaluation Board 

Test B 

The following preliminary statement on Test B was prepared 
by the Joint Chiefs of Staff's Evaluation Board immediately fol- 
lowing Test B. The statement was released by the White House 
on August 2, 1946. 


Supplement to Preliminary Report on Test "A" 
In general, the observations on ship damage presented by this 
board in its first report were confirmed by engineering surveys. 
The location of the bomb burst, accurately determined from photo- 
graphs, was such that only one ship was within 1,000 feet of the 
surface point over which the bomb exploded. There were about 
20 ships within half a mile, all of which were badly damaged, many 
being put out of action and five sunk. It required up to 12 days to 
repair all of those ships left afloat sufficiently so that they could 
have steamed under their own power to a major base for repair. 
It is now possible to make some estimate of the radiological in- 
juries which crews would have suffered had they been aboard Test 
"A" target vessels. Measurements of radiation intensity and a 
study of animals exposed in ships show that the initial flash of 
principal lethal radiations, which are gamma-rays and neutrons, 
would have killed almost all personnel normally stationed aboard 
the ships centered around the air burst and many others at greater 
distances. Personnel protected by steel, water, or other dense ma- 
terials would have been relatively safe in the outlying target vessels. 
The effects of radiation exposure would not have incapacitated 
all victims immediately, even some of the most severely affected 


might have remained at their stations several hours. Thus it is pos- 
sible that initial efforts at damage control might have kept ships 
operating, but it is clear that vessels within a mile of an atomic 
bomb air burst would eventually become inoperative due to crew 


Observations on Test "B" 

The Board divided into two groups for the observation of Test 
"B." Four members, after surveying the target array from the 
air, witnessed the explosion from an airplane eight miles away at 
an altitude of 7,500 feet. The other three members inspected the 
target array from a small boat the day before the test and observed 
the bomb's explosion from the deck of the USS HAVEN, 11 miles 
at sea to the east of the burst. 

The Board reassembled on the HAVEN on July 26, and the 
members have since examined photographs, data on radioactivity, 
and reports of other phenomena, and have inspected some of the 
target vessels. They have also consulted with members of the Task 
Force technical staff. 

As scheduled, at 0835 Bikini time on July 25, a bomb was 
detonated well below the surface of the lagoon. This bomb was 
suspended from LSM-60, near the center of the target array. The 
explosion was of predicted violence, and is estimated to have 
been at least as destructive as 20,000 tons of TNT. 

To a degree which the Board finds remarkable, the visible phe- 
nomena of explosion followed the predictions made by civilian and 
service phenomenologists attached to Joint Task Force One. At 
the moment of the explosion, a dome, which showed the light of 
incandescent material within, rose upon the surface of the lagoon. 
The blast was followed by an opaque cloud which rapidly enveloped 
about half of the target array. The cloud vanished in about two 
seconds to reveal, as predicted, a column of ascending water. From 
some of the photographs it appears that this column lifted the 
26,000-ton battleship ARKANSAS for a brief interval before the 
vessel plunged to the bottom of the lagoon. Confirmation of this 
occurrence must await the analysis of high-speed photographs 
which are not yet available. 

The diameter of the column of water was about 2,200 feet, and 
it rose to a height of about 5,500 feet. Spray rose to a much 
greater height. The column contained roughly ten million tons of 


water. For several minutes after the column reached maximum 
height, water fell back, forming an expanding cloud of spray which 
engulfed about half of the target array. Surrounding the base of 
the column was a wall of foaming water several hundred feet high. 

Waves outside the water column, about 1,000 feet from the 
center of explosion, were 80 to 100 feet in height. These waves rap- 
idly diminished in size as they proceeded outward, the highest 
wave reaching the beach of Bikini Island being seven feet. Waves 
did not pass over the island, and no material damage occurred 
there. Measurements of the underwater shock wave are not yet 
available. There were no seismic phenomena of significant magni- 

The explosion produced intense radioactivity in the waters of 
the lagoon. Radioactivity immediately after the burst is esti- 
mated to have been the equivalent of many hundred tons of 
radium. A few minutes exposure to this intense radiation at its 
peak would, within a brief interval, have incapacitated human 
beings and have resulted in their death within days or weeks. 

Great quantities of radioactive water descended upon the ships 
from the column or were thro\\ai over them by waves. This highly 
lethal radioactive water constituted such a hazard that after foui- 
days it was still unsafe for inspection parties, operating within a 
well-established safety margin, to spend any useful length of time 
at the center of the target area or to board ships anchored there. 

As in Test "A," the array of target ships for Test "B" did not 
represent a normal anchorage but was designed instead to obtain 
the maximum data from a single explosion. Of the 84 ships and 
small craft in the array, 40 were anchored within one mile and 20 
within about one-half mile. Two major ships were sunk, the battle- 
shijj ARKANSAS immediately and the heavy-hulled aircraft car- 
rier SARATOGA after 71/0 hours. A landing ship, a landing craft, 
and an oiler also sank immediately. The destroyer HUGHES, in 
sinking condition, and the transport FALCON, badly listing, were 
later beached. The submerged submarine APOGON was sent to the 
bottom emitting air bubbles and fuel oil, and one to three other 
submerged submarines are believed 16 have sunk. Five days after 
the burst, the badly damaged Japanese battleship NAGATO sank. 
It was found impossible immediately to assess damage to hulls, 
power plants and machinery of the target ships because of radio- 
active contamination. Full appraisal of damage will have to 
await detailed survey by engineer teams. External observation 
from a safe distance would indicate that a few additional ships 
near the target center may have suffered some hull damage. There 


was no obvious damage to ships more than one-half mile from the 


Observations and Conclusions, Both Tests 

The operations of Joint Task Force One in conducting the tests 
have set a pattern for close, effective cooperation of the Armed 
Services and civilian scientists in the planning and execution of 
this highly technical operation. Moreover, the tests have provided 
valuable training of personnel in joint operations requiring great 
precision and coordination of effort. 

It is impossible to evaluate an atomic burst in terms of con- 
ventional explosives. As to detonation and blast effects, where the 
largest bomb of the past was effective within a radius of a few 
hundred feet, the atomic bomb's effectiveness can be measured in 
thousands of feet. However, the radiological effects have no parallel 
in conventional weapons. It is necessary that a conventional bomb 
score a direct hit or a near miss of not more than a few feet to cause 
significant damage to a battleship. At Bikini the second bomb, 
bursting under water, sank a battleship immediately at a dis- 
tance of well over 500 feet. It damaged an aircraft carrier so that 
it sank in a few hours, while another battleship sank after five days. 
The first bomb, bursting in air, did great harm to the superstruc- 
tures of major ships within a half-mile radius, but did only minor 
damage to their hulls. No ship within a mile of either burst could 
have escaped without some damage to itself and serious injury to 
a large number of its crew. 

Although lethal results might have been more or less equivalent, 
the radiological phenomena accompanying the two bursts were 
markedly different. In the case of the air-burst bomb, it seems cer- 
tain that unprotected personnel within one mile would have suf- 
fered high casualties by intense neutron and gamma radiation as 
well as by blast and heat. Those surviving immediate effects would 
not have been menaced by radioactivity persisting after the burst. 

In the case of the underwater explosion, the air-burst wave 
was far less intense and there was no heat wave of significance. 
Moreover, because of the absorption of neutrons and gamma rays 
by water, the lethal quality of the first flash of radiation was not 
of high order. But the second bomb threw large masses of highly 
radioactive water onto the decks and into the hulls of vessels. These 
contaminated ships became radioactive stoves, and would have 


burned all living things aboard them with invisible and painless but 
deadly radiation. 

It is too soon to attempt an analysis of all of the implications 
of the Bikini tests. But it is not too soon to point to the necessity 
for immediate and intensive research into several unique problems 
posed by the atomic bomb. The poisoning of large volumes of water 
presents such a ])roblem. Study must be given to procedures for 
protecting not only ships' crews but also the populations of cities 
against such radiological effects as were demonstrated in Bikini 

Observations during the two tests have established the general 
types and range of effectiveness of air and shallow underwater 
atomic-bomb bursts on naval vessels, army materiel, including a 
wide variety of Quartermaster stores, and personnel. From these 
observations and from instrumental data it will now be possible 
to outline such changes, not only in military and naval design but 
also in strategy and tactics, as future events may indicate. 

National security dictates the adoption of a policy of instant 
readiness to defend ourselves vigorously against any threat of 
atomic weapon attack at any time and adherence to this policy 
until it is certain that there can never be an atomic war. One en- 
during princii)le of war has not been altered ])y the advent of the 
atomic weapon. Offensive strength will remain the best defenses. 
Therefore, so long as atomic bombs could conceivably be used against 
this country, the Board urges the continued production of atomic 
material and research and development in all fields related to 
atomic warfare. 


Appendix 12 

Preliminary Statement by the Evaluation 

Commission on 

Test A 

The following preliminary statement on Test A was prepared 
by the President's Evaluation Commission immediately following 
Test A. The statement was released by the White House on July 
11, 1946. 

Dear Mr. President: 

Your Evaluation Commission, divided between positions at sea 
and in the air, witnessed the First Bikini Test, at 33 seconds after 
9 :00 A.M., local time on July 1st, and has since completed a sur- 
vey of the damage. The Second Test, wherein the bomb will be 
exploded under water, will in some respects be of even greater 
interest, for it will have no precedent. 

The report of your Commission required by its directives of 
May 18th must await the assembling of considerable data deriving 
from instrumental and photographic measurements and analysis 
of tission product samples. However, we believe that it lies within 
the scope of your directive and may be of possible assistance to 
you, to submit, now, the following brief observations made from 
the layman's point of view, but with such accuracy as is presently 
available : 

1. The organization and execution of the operation was mag- 
nificently handled and has commanded our continuous admiration. 
The bomb was dropped under favorable weather conditions about 
30 seconds after the time set. The greatest credit is due Admiral 
Blandy and the officers and enlisted personnel of both services 
who, with scientists and other civilians, have served and are serv- 
ing under him with a display of team work that must be seen to 
be fully appreciated. 

2. Their conservatively safe distance from the burst led many 
observers to entertain an initial opinion that the bomb employed 
was somewhat under par. It is now, however, safe to state that 
the energy was of the same order of magnitude as in the case of 
previous atomic detonations, between the highest and lowest of this 
bomb's three predecessors. 


3. The accuracy of the drop was such that the explosion oc- 
curred within the area included within the allowance for the prob- 
able error of the elevation of drop, and detonation was probably 
within 100 feet of the chosen altitude. Nevertheless, the explosion 
actually occurred several hundred yards west of a point directly 
above the target ship NEVADA and therefore entirely west of the 
closely spaced array of capital ships. 

4. There were 90 targets anchored in the lagoon when the bomb 
exploded. These were not in battle formation but were placed in 
positions to give the largest amount of desired technical information 
with especially close concentration around the center target point. 
Those ships anchored a mile or more from the point of drop largely 
escaped injury. Those within a mile were sunk or suffered damage 
varying with the distance from the point of detonation and with 
the type of ship construction. On explosion, a destroyer and two 
transports sank promptly. A second destroyer and the Japanese 
cruiser SAKAWA sank within twenty-seven hours. The light car- 
rier INDEPENDENCE was gutted with fire and resultant explo- 
sions. The submarine SKATE was heavily damaged and later 
towed away. All of these were near the point of explosion. The 
other ships, including the only two capital ships which were within 
one-half mile of the detonation, received damage that would re- 
quire more or less complete overhaul and in most cases repair 
at major bases before they could again be used in combat. A 
study of this damage will point the way to changes in design which 
should minimize damage from blast and heat. Beyond these ships 
there was extensive damage to superstructure, radar, and fire con- 
trol. Had the ships within the damage area been manned, casualties 
and psychological injuries would have required a large percentage 
of replacements. Until the readings of complex instruments and 
the future life history of animals within the ships have been de- , 
termined no accurate appraisal of potential damage to humans 
within the ships can be made. 

5. No wave or blast damage could be noticed on Bikini Island, 
which is approximately three miles from the point of detonation. 

6. We are of the unanimous opinion that the first test amply 
justified the expenditure required to conduct it and that the second 
test is equally desirable and necessary. You made a wise decision 
when you approved the plans for these tests and they have been 
carried out with extraordinary skill, diligence and ingenuity. The 
test just completed has again proven that the atomic bomb is a 
weapon of terrific power when used on land or sea. 


Appendix 13 

Preliminary Statement by the Evaluation 
Commissionon on 
Test B 

The following preliminary statement on Test B was prepared 
by the President's Evaluation Commission immediately following 
Test B. The statement was released by the White House on August 
2, 1946. 

Dear Mr. President : 

Your acknowledgment on July 7th of our preliminary report 
on the tirst test at Bikini was much appreciated. 

The second test was conducted in the same area, July 25, local 
time, and on the same target ships less those sunk in the first test. 
The bomb was exploded under a moderate depth of water at 8 :30, 
a.m., local time, on schedule. Weather conditions were perfect. Seven 
members of your committee witnessed the results from the USS 
HAVEN stationed 11 miles from the point where the bomb ex- 
ploded. There was no requirement of dark glasses for this test, and 
the target ships were readily visible to the naked eye and easily 
distinguishable with the aid of binoculars. 

Our previous report endeavored to express our appreciation 
of the cooperation, assistance and unfailing courtesy extended by 
Admiral Blandy and by the officers and enlisted men and civilian 
scientific personnel of Joint Task Force One. Throughout, this 
attitude of interest and diligence has remained at the same high 
level, and the effect of longer observation of operations and better 
acquaintance with officers and men has been to convince us that 
you and the people of the United States can place the utmost re- 
liance on the fairness, thoroughness and real effort for the maximum 
of honest information which has characterized these tests. This 
disposition has expedited and lightened our task in complying 
with your directive. These tests have consistently adhered to the 
stated purpose of the mission : ' ' Primarily to determine the effects 
of the atomic bomb on naval vessels in order to gain information 
of value to the national defense." 

In the interval between tests the target ships were redeployed 
in respect to the point chosen for the second explosion so as to fur- 


nish maximum scientific and technical information from expected 

When the bomb exploded, the battleship ARKANSAS, nearest 
to the center of impact, and three other smaller ships sank at once. 
The aircraft carrier SARATOGA, also placed close by, sank 71/0 
hours later. As soon as radioactivity lessened sufficiently to permit 
safe operations, the destroyer HUGHES and the attack transport 
FALLON were beached to prevent their possible sinking. Of the 
eight submarines involved, six were submerged. Several of these 
appear to be injured and one at least has gone to the bottom. The 
two on the surface are not noticeably injured. All but a few of the 
target ships were drenched with radioactive sea water, and all 
within the zone of evident damage are still unsafe to board. It 
is estimated that the radioactivity dispersed in the water was the 
equivalent to that from many hundred tons of radium. 

We believe that interesting distinctions between the general 
results of the two explosions can even now be drawn without 
the risk of serious error. Both explosions sank several ships. 
From the limited observations we have thus far been able to make, 
the ships remaining afloat within the damage area appear to have 
been more seriously damaged by the aerial explosion than by the 
submarine explosion. The damage to ships in the first test might 
have been far greater if the bomb had exploded directly over the 
target ship, the NEVADA. 

In the first test much of the personnel within the ships would 
have received fatal doses of neutrons and gamma rays from the 
first deadly flash. On the other hand, the deadly effects of persistent 
radioactivity would have been much more severe in the second 
test. Had the target array been manned, it seems clear that casual- 
ties and both physical and psychological injury to personnel would 
have been very great. Rescue and attention to casualties would be 
difficult and dangerous. Within 2000 yards of explosion, ships would 
probably have been inoperative and a lapse of weeks might well 
ensue before relatively undamaged ships could again be used in 

The second bomb caused a deluge of water loaded with deadly 
radioactive elements over an area that embraced 90 per cent of the 
target array. Such results might be as disastrous to the fleet as 
results of the first test, although in part for different reasons. 
An enemy possessed of two or more bombs might well so dispose 
them as to create simultaneously the deadly features of both tests. 
Such tactics might effectively dispose of a fleet for many months ; 
for example, consider a Pearl Harbor attack on these lines. 


The results of both tests are already under study by the Bureau 
of Ships and will undoubtedly point the way to changes in ships' 
size, design and structure, both above and below the water line. 
Such changes can offer increased immunity to flash and blast effect, 
but protection from catastrophe by deadly gamma and neutron 
radiations lies rather in wide spacing of task forces and decentral- 
ization of navy yards, repair and loading facilities, of ships within 
ports, and amongst all available harbors. We are convinced distance 
is the best defense. 

As was demonstrated by the terrible havoc wrought at Hiro- 
shima and Nagasaki, the Bikini tests strongly indicate that future 
wars employing atomic bombs may well destroy nations and change 
present standards of civilization. To us who have witnessed the 
devastating effects of these tests, it is evident that if there is to be 
any security or safety in the world, war must be eliminated as a 
means of settling differences among nations. 


Appendix 14 

Test C (Cancelled) 

Prior to its cancellation by the President, the proposed "Test 
C" was the center of much discussion. In this test an atomic bomb 
was to be exploded at great depth beneath the surface of the 

Persons favoring holding such a test believed that it would 
produce an underwater shockwave of almost incredible violence. 
Ships might be crushed at ranges not equaled by explosions in air 
or by shallow-underwater explosions. Involving an entirely new 
kind of explosion, the test might till a large gap in physicists' under- 
standing of explosion phenomena. Would a great "gas bubble," 
hundreds of yards in diameter, break through the surface? Or 
would the surface remain unbroken? Would great waves be pro- 
duced? Some cynics, believing that this type of test would pro- 
duce the most damage, thought the Navy would try to avoid it. 

To many persons it was clear that this test would be less im- 
portant than the other two. On the technical side it was obvious 
that little or no thermal radiation would reach the surface. Neutron 
and gamma radiations also would be almost completely muffled by 
the intervening layer of water. The tactical considerations were 
even more pertinent. Nearly all harbors are shallow ; most coastal 
waters are shallow. Thus a deep underwater explosion could never 
be used in these important regions. It would be applicable only 
in the open ocean, and here, of course, a fleet could be dispersed as 
widely as necessary so that only one or two ships could be sunk 
by one atomic bomb. 

Nevertheless, plans were made to hold Test C, and a considerable 
amount of preparatory work was done. Studies were made as to 
how to position the target ships accurately. Anchoring being im- 
practical in very deep water, thought was given to "streaming" 
the ships. They could be fastened to a small island by means of 
long cables, and then allowed to take up more or less fixed positions 
determined by the direction of the ocean currents and by the 
lengths of the cables. Or perhaps the ships could be powered and 
underway, steered by radio. Work was started also on methods of 
lowering the bomb to the desired depth, holding it in the desired 
position despite the ocean currents, and firing it. It was expected 
that the test would be held near Bikini Atoll, and construction 
crews went to work preparing necessary installations there. 


But the success of the first two tests, together with the increas- 
ing shortage of military personnel and available civilian scientists, 
caused reconsideration of the desirability of holding this third 
test. And on September 7, 1946, President Truman, acting with 
the advice of the Joint Chiefs of Staff, postponed the test indefi- 
nitely. His statement was as follows : 

"In view of the successful completion of the first 
two atomic bomb tests of Operation Crossroads and 
the information derived therefrom, the Joint Chiefs 
of Staff have concluded that the third explosion, Test 
C, should not be conducted in the near future. . . . 

"The additional information of value expected to 
result from Test C is such that the Joint Chiefs of 
Staff do not feel that completion of the test in the near 
future is justified." 


Appendix 15 

Chronology of Atomic Bomb Detonations 

Five atomic bombs liave been detonated to date. The times and 
places of tlieir detonation are as follows : 



Alamogordo, N. M. 


MWT : July 16, 1945, at 5 :30 a.m. 
EWT : July 16, 1945, at 7 :30 a.m. 
GOT : July 16, 1945, at 11 :30 a.m. 

Local Time : Aug. 6, 1945, at 8 :15 a.m. 
EWT : Aug. 5, 1945, at 7 :15 p.m. 
GOT : Aug. 5, 1945, at 11 :15 p.m. 

Local Time: Aug. 9, 1945, at 10:58 

EWT : Aug. 8, 1945, at 9 :58 p.m. 
GOT : Aug. 9, 1945, at 1 :58 a.m. 

Local Time: July 1, 1946, at 34 
seconds after 9 :00 a.m. 

EST: June 30, 1946, at 34 seconds 
after 5 :00 p.m. 

GOT : June 30, 1946, at 34 seconds 
after 10 :00 p.m. 

Bikini (underwater) Local Time: July 25, 1946, at 59.7 

seconds after 8 :34 a.m. 

EST: July 24, 1946, at 59.7 seconds 
after 4.34 p.m. 

GCT : July 24, 1946, at 59.7 seconds 
after 9 :34 p.m. 

2 Hiroshima, Japan 

3 Nagasaki, Japan 

4 Bikini (in air) 



A-Day, 23, 104 

A-Day, miss, 71, 114 

Aerology, see Meteorology 

Aircraft, 98, 127 

Alamogordo, 6 

Alpha particles, see Radiation, alpha 

Ammunition, 13, 125 

Animals, 50, 84, 129, 140, 166 

Army, see War Department 

Army Air Forces, 97 

B-Day, 1, 150 

Ball-of-Fire, see Fireball 

Base Surge, 159 

Beta particles, see Radiation, beta 

Bikini Atoll 

choice of, 17 

damage to, 163 

map of, 18, 19, 89 
Bombs, chronology, 207 
Burst, see Detonation 

Cameras, 78, 148, 152 

Cauliflower, 156 

Chief of Staff, 29 

Chronology, see Bombs, chronology of 

Cloud, condensation, 115 

Column, 155 

Commander Joint Task Force One, 12 


observers from, 39, 186 
Contamination, 159, 166 
Correlation of damage and cause of 

damage, 127 
Crater, 160 
Crews, injury to, see Personnel 


terms for expressing, 130 

to materiel, 127, 138 

to ships, 125, 130-135, 164-166 
Data, see Oceanography, Pressure, 

Radiation, etc. 
David Taylor Model Basin, 67 
Decontamination, 169 
Deputy Task Force Commander for 

Aviation, 29 
Deputy Task Force Commander for 

Technical Direction, 28, 97 


Test A, 108 

Test B, 151 
Director of Ship Material, 47 
Dogs, 85 
Dome, 154 

Drone boats, 128, 168 
Drone planes, see Aircraft 

Energy release, 152 

Equipment, see Material 

Errors, see A-Day Miss, Timing Signal 

Evaluation Board 

creation, 15, 182 

membership, 182 

preliminary reports, 193, 196 
Evaluation Commission 

creation, 40, 184 

membership, 184 

preliminary reports, 199, 202 
Explosion, see Detonation 

Fall-out, 152 

Fillet, 157 

Fireball, 116 

Fires, 129 

Fish, 92, 163 

Fish and Wildlife Service, see Interior 

Fission products, 81, 108, 120 
Force Organization, 96 
Fuel loads, 13 

Gages, 62-71, 111, 148, 162 
Gamma radiation, see Radiation, 

Genetic effects, see Mice 
Geological survey, 87 
Goats, 84, 140 
Ground Forces Adviser, 29 
Guinea pigs, 84 

Heat, see Radiation, thermal 
Hiroshima, 6, 28 
How hour 

Test A, 104 

Test B, 151 
Hulls, 131, 132 


Illumination, see Eadiation, optical 
Immobilization, see Damage 
Impulse, 71, 114 
Infrared radiation, see Radiation, 

optical ; Radiation, thermal 
Injury, see Damage, Animals, Goats, 

Intelligence, 33 
Interior Department, 20 

Joint Chiefs of StaflE, 11, 33 
Joint Crossroads Committee, 181 
Joint Staff Planners, 11 
Joint Task Force One 

creation, 13, 25 

directive, 14-15 

dissolution, 172 

organization, 96, 173 

LeMay Subcommittee, 11, 28 
Lethal radius, see Damage 
Light, see Radiation, optical 
Logistics, 41 
Los Alamos Laboratory, 9 

Mach Stem, 61 

Manhattan Engineer District, 12, 28 

see also Los Alamos Laboratory 

Bikini Atoll, 89 

Marshall Islands, 19 

Pacific Ocean, 18 

Target layout for Test A, 126 
Marine life, see Fish 
Marshall Islands 

history, 17 

map, 19 

damage to, 139 

exposure of, 138-140 
Meteorology, 102, 150 
Mice, 84, 143 
Mike hour 

Test A, 109 

Test B, 151 
Mushroom, 118 

Nagasaki, 6 

Navy Department, 8, 14 
Nuclear radiation, see Radiation, 

Objects of tests, 14 


Congressional, 39, 186 

Evaluation Board, 40, 182 

Evaluation Commission, 41, 184 

United Nations, 39, 185 

others, 36 
Oceanography, 22, 161, 169 
Operation Crossroads, code name of, 

Operation plan, 43 
Optical radiation, see Radiation, 


Pacific Ocean 

map, 18 

injury to, 48 

recruiting of, 30 
Photography, 32, 50, 74 

see also Cameras 
Pigs, 84 
Planning, 40 

Plume, see Mushroom, Column 
Plutonium, 81 
President, 13 
President's Evaluation Commission, 

see Evaluation Commission 
Press, 36 

in air, 60, 110, 111 

in water, 153 
Public relations, 34 
Purpose, see Object of tests 

Queen day, see Rehearsals 


alpha, 80, 121 

beta, 80, 108, 121 

gamma, 80, 83, 121, 127, 141, 153 

neutron, 108, 121, 152 

nuclear, 80, 82, 121 

optical, 74, 108, 116 

thermal, 127, 152 
Radio, 40 

Radioactivity, 45, 167 
Radiological safety, 31, 124, 128, 141, 

168, 170 
Radiological Safety Adviser, 170 
Radiological Safety School, 170 
Rats, 84 

for Test A, 45, 102, 105 

for Test B, 45, 150 


Remote measurements, 59 
Reports, see Evaluation Board, 
Evaluation Commission 

Safety Adviser, 47 

Security, 33 

Ship design, 3 

Sliip parts, see Damage 

Ships, see Vessels 


in air, 72, 109, 127, 144, 157 

in water, 109, 153, 157 
Site, see Bikini Atoll 
Sodium, 153 
Sound, 110 
Steel, 144 

Target array 

Test A, 106, 126 

Test B, 146 
Task Groups, see Force organization 
Technical Director, 47, 57 
Temperature, 117 
Termination of operation, 171 
Test A, 23, 104 
Test B, 24, 145, 151 
Test C, 205 
Thermal radiation, see Radiation, 

Timing signal failure, 113 
Trinity, see Alamogordo 

Ultraviolet radiation, see Radiation, 

United Nations observers, 39, 185 
Uranium, 81 


anchoring, 96, 147 

authorization to use, 14 

decontamination, 169 

German, 55 

inspection, 55 

Japanese, 52, 55, 132, 165 

preparation, 46, 50, 147 

watertightness, 52 

see also Damage, Ship design 
Visible radiation, see Radiation, 


War Department, 14, 97 

see also Army Air Forces, Man- 
hattan Engineer District 


currents in, 169 

radioactivity in, 170 

see also Shockwave, Waves 

Waves, 22, 147, 160 

Weather, see Meteorology 

William day, see Rehearsals 

Winds, see Meteorology 


definitions, 66 
locations, 109, 143 


Adams, Major W. B'., 104 
Anderson, Captain G. W., Jr., 12 
Anderson, Ensign D. L., 104 
Archer, Ensign H. M., 58 
Arnold, General H. H., 10, 11 
Arons, Dr. A. B., 63 
Ashworth, Captain F. L., 46 
Atanasoff, Dr. J. V., 63 
Ballard, Commander S. S., 63, 75, 76 
Barnes, Lieutenant Commander C. A., 

Betts, Brigadier General T. J., 30, 33, 

34, 38 
Bishop, Captain J. E., 48 
Blakelock, Brigadier General D. H., 


Blanchard, Colonel W. J., 104 
Blandy, Vice Admiral W. H. P., 12, 13, 

21, 27, 35, 42, 48, 96, 150, 165 
Bonesteel, Colonel C. H., 12 
Borden, Brigadier General W. A., 11 
Brodie, Captain Robert, Jr., 29, 32 
Chamblin, Lieutenant J. H., 148 
Chenchar, Captain Paul, Jr., 104 
Cothran, Sergeant J. W., 105 
Cumberledge, Captain A. A., 40, 150 
Davis, Captain W. P., 97 
Debenham, Lieutenant Commander 

J. K., 58 
Dessauer, Dr. G., 170 
Draeger, Captain R. H., 84, 87, 140, 

141, 143, 166 ■ 


Engelman, Captain C. L., 138 
Fahrion, Rear Admiral F. G., 97 
Forbes, Professor Alexander, 148 
Frederick, Colonel J. D., 97, 138 
Ganey, Colonel W. D., 40 
Gentry, Captain K. M., 40 
Gilbert, Captain, 17 
Giles, Lieutenant General B. M., 10 
Giltillan, Commander E. S., 58 
Glenn, Lieutenant R. M., 104 
Harrison, Captain W. C, Jr., 104 
Hartmann, Dr. G. K., 64, 67 
Henderson, Dr. J. E., 63, 146 
Holloway, Dr. M. G., 150, 151 
Holter, N. J., 22, 147 
Holzman, Colonel B. J., 40, 150 
Isaacs, J. D., 148 
Iverson, H. W., 148 
Juda, 93 

KautFman, C )mmander D. L., 170 
Kepner, Major General W. E., 29 
King, Admiral E. J., 10, 11 
Lampson, Dr. C. W., 63 
Leahy, Admiral W. D., 10 
Lee, Captain Fitzhugh, 34, 35, 37, 38 
LeMay, Major General C. E., 10, 11 
Lonnquest, Captain T. C, 138 
Lowry, Rear Admiral F. J., 30 
Lyman, Captain C. H., 30, 40 
Lyon, Captain G. M., 47, 48, 170 
Lyon, Dr. W. K., 148 
Lyons, Corporal H. B., 104 
Lyttle, Captain G. H., 99 
McAuliffe, Major General A. C, 29 
McFarland, Brigadier General A. J., 

Mach, Ernst, 61 
McKeehan, Captain L. W., 63 
McMahon, Senator Brien, 10 
McReynolds, Commander A. W., 58 
Manguni, Seaman First Class R. L., 48 
Marshall, Captain, 17 
Marshall, General G. C, 10 
Modlin, Corporal R. M., 104 
Moran, Radioman First Class J. D., 48 
Morris, Lieutenant Commander F. G., 



Mott, Captain E. B., 138 

O'Brien, Dean M. P., 148, 161 

O 'Brien, Professor Brian, 79 

Orr, Chief Warrant Officer J. P., 63 

Parker, Captain E. N., 99 

Parsons, Rear Admiral W. S., 12, 28, 

46, 48, 97, 135, 150, 172 
Penney, Dr. W. G., 62, 63, 64 
Pool, Dr. M. L., 170 
Pottle, Captain V. L., 12 
Quackenbush, Captain R. S., 38, 74 
Ramey, Brigadier General R. M., 98, 

Reagan, Seaman First Class J. R., 48 
Revelle, Commander Roger, 161, 169 
Riddle, Captain F. L., 58 
Rivero, Captain Horacio, 46 
Roth, Lieutenant Colonel A., 170 
Sawyer, Dr. R. A., 47, 57, 58, 59, 101 
Semple, Captain David, 105 
Sklaw, Lieutenant C, 148 
Smith, Colonel H. B., 39 
Smith, L. D., 104 

Snackenberg, Commodore J. A., 29, 30 
Solberg, Rear Admiral T. A., 47, 49, 

52, 54, 169 
Spaatz, Lieutenant General C. A., 10 
Sprague, Rear Admiral C. A. P., 99 
Stephenson, Dr. R. J., 170 
Sutherland, Colonel J. R., 104 
Swancutt, Major W. P., 104, 105 
Talbot, Lieutenant Colonel J. M., 170 
Thatcher, Dr. E. W., 58 
Titterton, Dr. E. W., 151 
Truman, President Harry S., 9, 13, 31, 

Uehlinger, Captain A. E., 64 
Vine, A. C, 148 
Warner, R. S., Jr., 101, 150 
Warren, Captain Shields, 87, 141 
Warren, Colonel S. L., 48, 49, 80, 82 
William, Lieutenant W. H., 48 
Williams, Commander E. G., 170 
Wilson, C. T. R., 115 
Wood, Major H. H., 104 
Wyckoff, Dr. C. W., 145, 146 














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