The motives behind the Crusades were political as well as religious. Why was this the case? (950-1100)

The Crusades were a series of religious and political wars fought between 1096 and 1291 for control of the Holy Land. Pope Urban II initiated the First Crusade (1096-1102) in order to aid the Christian Byzantine Empire, which was under attack by Muslim Seljuk Turks. As a result of this crusade, Europeans captured Jerusalem in 1099. Muslims quickly unified against the Christian invading and occupying force and the two groups battled in subsequent wars for control of the Holy Land. By 1291 the Muslims firmly controlled Jerusalem and the coastal areas, which remained in Islamic hands until the twentieth century.