AGE OF THE CRUSADES. Except in Spain, where the Kings of Leon had gradually reconquered a fourth part of the peninsula, Christian Europe had remained for nearly three centuries on the defensive against Islam. In the eleventh century a new and ruder people, the Seljuk Turks, became dominant in Mohammedan Asia, maltreated Christian pilgrims, and conquered Asia Minor (1071). At the appeal of the Greek Emperor, Pope Urban II. called Christian Europe to arms (1095) ; and before the close of the century a great host of crusaders had marched through Asia Minor and occupied Syria, establishing there a kingdom of Jerusalem and other principalities. (See CRUSADES.) The struggle thus opened con tinued for two centuries. The retainers of the Christian princes in Syria and the military monks (see HOSPITALERS; TEMPLARS, KNIGHTS; TEU TONIC KNIGHTS) constituted the standing army of the Christians; repeated crusades from all parts of Europe brought volunteer assistance. Thestrug gle ended at the close of the thirteenth century with the evacuation of Syria by the Christians. An episode of the Crusades was the temporary overthrow of the Greek Empire (1204) by French crusaders in alliance with Venice. A Flemish count (see BALDWIN I.) was made Emperor at Constantinople, and the European territories of the Empire were assigned to French kings and dukes or to the Doge and Commune of Venice.
The Greek emperors, meanwhile, continued to reign in Asia Minor; and in the latter half of the century, with the aid of the Genoese. they recovered Constantinople (1261) and the greater part of their former possessions. The Venetians, however, kept much of the territory they had acquired, and became the leading commercial power in the eastern Levant; aJthough the Geno ese, on better terms with the Greeks, had control of trade in the Black Sea. The only permanent gains made by Christendom during these centu ries were in Spain and on the Baltic. War against the heathen in these places also was re garded as a crusade. By the middle of the thir teenth century the Christians had conquered all of Spain except Granada ; the Teutonic Knights had subdued and converted the Prussians; and another body of military monks, the Brethren of the Sword, were doing the same work in Livonia and Esthonia. In this same century, however, Christendom lost ground in eastern Europe through the conquest of Russia by the Mongols. See MONGOLIAN RACE.