August 15, 1096
Jerusalem has been controlled for about 60 years by Muslim Seljuk Turks, who established peaceful coexistence with Byzantine Christians in Jerusalem. But that peaceful relationship had deteriorated by the 1090s as the Turks and the Byzantines clashed over territory throughout the region. The Byzantine emperor, Alexius I Comnenus, sent a delegation to Pope Urban II in March 1095 to seek help from the Western Christian powers. On Nov. 27, 1095, the pope called for a crusade to liberate Jerusalem.
By the time the crusader armies begin moving east on the official start date of Aug. 15, 1096, the Fatimids have captured Jerusalem from the Seljuks, presenting a different Muslim opponent for the Christians. Also, several armies have left early, forming what becomes known as the People’s Crusade, although many of those forces never advance beyond Hungary. Meanwhile, the religious fervor stirred up by Urban II has spawned pogroms in Europe, and German peasants have slaughtered Jews across the Rhineland.
Up to 100,000 soldiers form the crusader army that gathers in Constantinople during the fall of 1096. Some are motivated to take back Jerusalem for Christianity. Some want to attain riches through conquest. Some are driven by both reasons.
The First Crusade captures and pillages Jerusalem on July 15, 1099, slaughtering Muslim residents and forcing Jews to accept new rulers. The crusaders repel an Egyptian army at Ashdod less than a month later to secure the conquest. Urban II dies July 19, 1099, before word of Jerusalem’s capture can reach him. The crusaders establish a kingdom under Baldwin in 1100.