THE WORLD TO-DAY 425 the field against the Central Powers (Germany and Austria), and the German attempt to enter France through Belgium (violating the treaty guaranteeing Belgian neutrality as a mere * scrap of paper') brought Great Britain and her Em- pire into the fray. Bulgaria and Turkey were soon en- tangled with Germany and Austria, while Italy, Greece, and the Arabs joined the Allies (England and France) one after another. But the most decisive factor which tilted the balance and fortunes of war against the Germans and their allies was the entry of the United States of America in 1917. In the Far East, Japan threw in her weight on the side of England as a result of the Anglo-Japanese alliance formed in 1902. Though in the course of human history longer wars (like the Hundred Years' War) had been fought, this Great War was unparalleled in its disastrous consequences. Not merely was it the first war in which the whole World was directly or indirectly involved, but it was also unique in its concen- tration of energies for the destruction of men and materials. It was the first war in human history to be fought in three dimensions, on account of the addition of the aerial arm and the submarine Science revealed for the first time its baleful potentialities. During those four years of arma- geddon Humanity appeared to strain every nerve to see through the struggle once and for all. The following sketch of one of its trying moments might convey to the reader a faint glimpse of its grim character : " In the low-lying plain of Flanders, where the British held Ypres salient against many German attempts to drive through to the channel ports, the warfare was partly amphibious since the trenches filled with water in the wet winter weather. At times, by day, there was hardly a sign of life above the ground, behind the barbed wire which protected the two lines of hostile trenches, with a No Man's Land of varying width between. Even