The First Crusade

Pope Urban II preached the crusade at the Council of Clermont on 27 November 1095, responding to an appeal from the Byzantine Emperor Alexios I Komnenos for military help against the Seljuk Turks, who had taken most of Byzantine Anatolia after their victory at Manzikert in 1071. Urban's sermon, known only through later and not entirely consistent reports, called on Western knights to set aside the private warfare that consumed so much of their energy at home and turn it instead toward liberating the Christians of the East and recovering Jerusalem, offering those who went a remission of the penance owed for their sins.

The response outran anything Urban had organized for. An unarmed and poorly provisioned popular movement under preachers including Peter the Hermit set out ahead of the main armies in what is remembered as the People's Crusade, and was destroyed by the Seljuks in Anatolia within months. The main crusader armies, drawn from France, Flanders, southern Italy and beyond, assembled separately through 1096 and 1097 and converged on Constantinople, where Alexios required their leaders to swear an oath to return any former Byzantine territory they recaptured to the empire, a promise that later became a major source of Byzantine-Latin friction.

The crusader armies crossed into Anatolia in 1097, defeated a Seljuk force at Dorylaeum, and reached Antioch in October, where an eight month siege ended with the city's capture in June 1098, days before a large relieving army arrived; a second siege, of the crusaders themselves now trapped inside the city, ended in a further crusader victory. The march south to Jerusalem, delayed by disputes among the crusade's leaders over who would hold Antioch, resumed the following year, and the city was placed under siege in June 1099.

Jerusalem fell to the crusaders on 15 July 1099. Contemporary Christian and later Muslim and Jewish accounts describe the sack that followed as a large scale killing of the city's Muslim and Jewish inhabitants, including people who had taken refuge in the city's mosques and synagogues; the figures given by medieval chroniclers are not independently verifiable and are treated with caution by modern historians, though the scale of the massacre itself is not disputed. Godfrey of Bouillon was chosen to rule the new Christian territory, taking the title Defender of the Holy Sepulchre rather than king, and the conquered lands were organized over the following years into four Crusader states: the Kingdom of Jerusalem, the County of Edessa, the Principality of Antioch and the County of Tripoli.