From the Hildebrandine revival sprang also the Crusades, and the combination of the military and religious ideals of the Latin world in the pursuit of a holy war for the recovery of Christ’s Sepulchre. The Turkish advance was checked; the Eastern Empire was saved from imminent destruction; and a series of Latin states in Syria and Greece extended the scope of western influence at the expense of Orthodox and Mohammedan alike. But the diversion of the Fourth Crusade to overthrow the Empire of Constantinople indicates the high-water mark of the Latin Christian power in the East; and the change in the current of western ideas made the Crusades of the thirteenth century but vain attempts to restore a vanished dream. Before the end of our period, the Christian domination in the East had shrunk to the lordship of a few Greek islands. The Palæologi brought back Byzantine rule to the Byzantine capital; and the strongest kings of the West could not save the remnants of the Latin states in Syria. The Mongol invasions threatened Christian and Saracen alike. While the western prospects were so fair, in the East barbarism was on the highway to ascendency. [Sidenote: The Feudal Age.] The failure of the Empire to rule the world led to a feudal reaction, that was not least felt in the lands directly governed by the Emperors. Our period witnesses both the triumph and the decay of feudalism. It is the time when feudal ideas prevailed all over the western world, following the Crusaders into the burning deserts of Syria, and the lands of the Eastern Emperors. The Normans took feudalism to southern Italy and Sicily, and developed the feudalism that they already found in England. Even Scandinavia evolved a feudalism of its own, and the sons and grandsons of the followers of William the Conqueror planted feudal states side by side with the Celtic tribalism of Wales and Ireland. For nearly four centuries the mail-clad feudal horseman was invincible in battle, and the stone-built feudal castle, ever becoming more complex and elaborate in structure, was impregnable except to famine. The better side of feudal social ideals—chivalry, knighthood, honour, and courtesy—did something to temper the brutality and pride of the average baron, and found powerful expression in the vernacular literatures, written to amuse nobles and gentry. But before our period ends, the days of feudal ascendency were over. Hopeful of triumph in Germany, where the German state suffered by its kings’ pursuit of the imperial vision, feudalism found in Italy a powerful rival in strong municipalities closely allied with the Church. In western Europe it was beginning to give ground. The greater feudatories crushed their lesser neighbours, and built up states that were powerful enough to stand by themselves. The Church, though fitting itself into the feudal organisation of society, could never repose simply on brute force. [Sidenote: The