THE DECLINE OF THE PAPACY 217
by the Holy See were principally two: Frederick had retained
Sicily for himself, although he had promised to detach it from
the Empire, and he had not kept his vow to serve in a
Crusade. The papacy felt that Frederick was becoming too
powerful, and Honorius made an alliance with the Guelph
cities of Italy against the Ghibelline Emperor. Honorius,
who had been Frederick's tutor, was disinclined to go further,
but his successor in 1227, Gregory IX, had no compunction
in excommunicating Frederick. The Emperor replied by
inciting the populace to eject Gregory from Rome. The
quarrel was settled in 1230, after Frederick's return from
Palestine, but a few years later the Holy See and the Empire
were again in dispute. In 1237 Gregory gave his blessing
to the Italian cities, which had renewed their struggle against
the Empire, and in 1239 Frederick struck at the Pope by
intervening in Sardinia, over which the papacy claimed
suzerainty. Frederick was excommunicated for the second
time, and showed his opinion of the Church by seizing a
number of cardinals and bishops.
Gregory died with the contest still undecided, but a com-
promise seemed probable with the installation of Pope
Innocent IV in 1243. The Church and Empire, however,
had no faith in each other, and, after long negotiations, the
truce between them was broken. In 1245, Innocent, pro-
nouncing Frederick unfit to rule because of his offences against
the Church, deposed him in the name of God and called on
the people to elect a new Emperor. Frederick fought
fiercely for his crown, and on his death, his son, Conrad IV,
took up the fight against the Church. The struggle lasted
throughout Conrad's reign with varying success, but on
balance with the advantage on the side of the Empire.
Conrad's infant son, Conradin, was the next Emperor (May,
1254). Manfred, Conradin's uncle, carried on the war
against the papacy, and in 1260 made himself master of Italy
by a great victory at Montaperti.