The Pope who initiated the First Holy Crusade was Pope Urban II. Pope Urban II was born Odo of Châtillon or Otho de Lagery. He lived from March 1088 to his death in 1099. He was a native of France and was a descendant of a noble family in Châtillon-sur-Marne. Reims was the nearby cathedral school that Urban (named Eudes of Châtillon at birth), began his studies in 1050.

At the beginning of his life in the church, he was prior of the abbey of Cluny. Later, Pope Gregory VII named him cardinal-bishop of Ostia c. 1080. He became one of the most prominent and active supporters of the Gregorian reforms, especially as legate in the Holy Roman Empire in 1084. Eudes was among the three whom Gregory VII nominated as papabile (worthy of being or eligible to be pope).

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 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. All of the actions culminated in July 1099 in the reconquest of Jerusalem and the establishment of the Kingdom of Jerusalem.

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