The First Crusade (1095–1099) was the first of a number of crusades that attempted to recapture the Holy Land, called for by Pope Urban II at the Council of Clermont in 1095. Urban called for a military expedition to aid the Byzantine Empire, which had recently lost most of Anatolia to the Seljuq Turks. The resulting military expedition of primarily French-speaking Western European nobles, known as the Princes’ Crusade, not only re-captured much of Anatolia but went on to conquer the Holy Land (the Levant), which had fallen to Islamic expansion as early as the 7th century, and culminated in July 1099 in the re-conquest of Jerusalem and the establishment of the Kingdom of Jerusalem.
The expedition was a reaction to the appeal for military aid by Byzantine Emperor Alexios I Komnenos. Urban’s convocation of the Council of Clermont was specifically dedicated to this purpose, proposing siege warfare against the recently occupied cities of Nicaea and Antioch, even though Urban’s speech at Clermont in the testimony of witnesses writing after 1100 was phrased to allude to the re-conquest of Jerusalem and the Holy Land as additional goals.
The successful Princes’ Crusade was preceded by the People’s Crusade, which was a popular movement instigated by Peter the Hermit in the spring of 1096. Mobs of peasants and laymen travelled to Anatolia where they came up against the Turks, on the way attacking populations of Jews in the Rhineland. They were decisively defeated at the Battle of Civetot in October.
The Princes’ Crusade, by contrast, was a well-organized military campaign, starting out in late summer of 1096 and arriving at Constantinople between November 1096 and April 1097. The crusaders marched into Anatolia, capturing Nicaea in June 1097 and Antioch in June 1098. They arrived at Jerusalem in June 1099 and took the city by assault on 7 July 1099, massacring the defenders. A brief attempt by the Saracens to recapture Jerusalem was repulsed at the Battle of Ascalon.
During their conquests, the crusaders established the Latin Rite crusader states of the Kingdom of Jerusalem, the County of Tripoli, the Principality of Antioch, and the County of Edessa. This was contrary to the wishes of the Eastern Rite Byzantines, who wanted the land that the Muslims took from them returned, rather than occupied by Latin Catholics. After the retaking of Jerusalem, most of the crusaders returned home. This left the crusader kingdoms vulnerable to Muslim reconquest during the Second and Third Crusades.