Pope military aid from Pope Urban II in the ongoing Byzantine–Seljuq wars. Urban, at the council of Clermont, called the First Crusade to assist the Byzantine Empire to regain the old Christian territories, especially Jerusalem. With the East–West Schism, the Eastern Orthodox Church and the Catholic Church split definitively in 1054. This fracture was caused more by political events than by slight divergences of creed. Popes had galled the Byzantine emperors by siding with the king of the Franks, crowning a rival Roman emperor, appropriating the Exarchate of Ravenna, and driving into Greek Italy. In the Middle Ages, popes struggled with
Pope Urban II than to his own desire that Jerusalem be freed from Muslim rule. It was believed that originally that Urban wanted to send a relatively small force to aid the Byzantines, however after meeting with two prominent members of the crusades Adhemar of Puy and Raymond of Saint-Guilles, Urban decided to rally a much larger force to retake Jerusalem. Urban II refers to liberating the church as a whole or the eastern churches generally rather than to reconquering Jerusalem itself. The phrases used are "churches of God in the eastern region" and "the eastern churches" (to the Flemish), "liberation of the