During the First Crusade, Christian knights from Europe capture Jerusalem after seven weeks of siege and begin massacring the city's Muslim and Jewish population.
Beginning in the 11th century, Christians in Jerusalem were increasingly persecuted by the city's Islamic rulers, especially when control of the holy city passed from the relatively tolerant Egyptians to the Seljuk Turks in 1071. Late in the century, Byzantine Emperor Alexius Comenus, also threatened by the Seljuk Turks, appealed to the West for aid. In 1095, Pope Urban II publicly called for a crusade to aid Eastern Christians and recover the holy lands. The response by Western Europeans was immediate.
The first crusaders were actually undisciplined hordes of French and German peasants who met with little success. One group, known as the "People's Crusade," reached as far as Constantinople before being annihilated by the Turks. In 1096, the main crusading force, featuring some 4,000 mounted knights and 25,000 infantry, began to move east. Led by Raymond of Toulouse, Godfrey of Bouillon, Robert of Flanders, and Bohemond of Otranto, the army of Christian knights crossed into Asia Minor in 1097.
In June, the crusaders captured the Turkish-held city of Nicaea and then defeated a massive army of Seljuk Turks at Dorylaeum. From there, they marched on to Antioch, located on the Orontes River below Mount Silpius, and began a difficult six-month siege during which they repulsed several attacks by Turkish relief armies. Finally, early in the morning of June 3, 1098, Bohemond persuaded a Turkish traitor to open Antioch's Bridge Gate, and the knights poured into the city. In an orgy of killing, the Christians massacred thousands of enemy soldiers and citizens, and all but the city's fortified citadel was taken. Later in the month, a large Turkish army arrived to attempt to regain the city, but they too were defeated, and the Antioch citadel surrendered to the Europeans.
After resting and reorganizing for six months, the crusaders set off for their ultimate goal, Jerusalem. Their numbers were now reduced to some 1,200 cavalry and 12,000 foot soldiers. On June 7, 1099, the Christian army reached the holy city, and finding it heavily fortified, began building three enormous siege towers. By the night of July 13, the towers were complete, and the Christians began fighting their way across Jerusalem's walls. On July 14, Godfrey's men were the first to penetrate the defenses, and the Gate of Saint Stephen was opened. The rest of the knights and soldiers then poured in, the city was captured, and tens of thousands of its occupants were slaughtered.
The crusaders had achieved their aims, and Jerusalem was in Christian hands, but an Egyptian army marched on the holy city a few weeks later to challenge their claim. The Egyptians' defeat by the outnumbered Christians in August ended Muslim resistance to the Europeans for the time being, and five small Christian states were set up in the region under the rule of the leaders of the crusade.