Thousands of people of all classes responded to Urban’s call, joining what became known as the First Crusade. The First Crusade was successful, mostly because of the dynamic enthusiasm of the participants, who had little more than religious zeal. They knew little of the geography or climate of the Middle East and could never agree on a leader. Adding to these disadvantages, supply lines were never set up, starvation and disease wracked the army, and the Turks slaughtered hundreds of noncombatants. Nevertheless, the army pressed on, besieging and taking several cities, including Antioch. After a monthlong siege, the Crusaders took Jerusalem in July 1099 (Map 14.2).

With Jerusalem taken, some Crusaders regarded their mission as accomplished and set off for home. Others stayed, setting up institutions to rule local territories and the Muslim population. Four small “Crusader states” — Jerusalem, Edessa, Tripoli, and Antioch — were established, and castles and fortified towns were built in these states to defend against Muslim reconquest.

Between 1096 and 1270 the crusading ideal was expressed in eight papally approved expeditions, though none after the First Crusade accomplished very much. The Muslim states in the Middle East were politically fragmented when the Crusaders first came, and it took them about a century to reorganize. They did so dramatically under Saladin (Salah al-Din), who unified Egypt and Syria. In 1187 the Muslims retook Jerusalem, but the Christians held onto port towns, and Saladin allowed pilgrims safe passage to Jerusalem. From that point on, the Crusader states were more important economically than politically or religiously, giving Italian and French merchants direct access to Eastern products.

After the Muslims retook Jerusalem, the crusading movement faced other setbacks. During the Fourth Crusade (1202–1204), Crusaders stopped in Constantinople, and when they were not welcomed, they sacked the city. The Byzantine Empire splintered into three parts and soon consisted of little more than the city of Constantinople. Moreover, the assault of one Christian people on another, made the split between the churches permanent and discredited the entire crusading movement in the eyes of many Christians.

In the late thirteenth century Turkish armies, after gradually conquering all other Muslim rulers, turned against the Crusader states. In 1291 the Christians’ last stronghold, the port of Acre, fell.