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 IV Pope Urban IV Pope Urban IV (; c. 1195 – 2 October 1264), born Jacques Pantaléon, was the head of the Catholic Church and ruler of the Papal States from 29 August 1261 to his death in 1264. He was not a cardinal; only a few popes since his time have not been cardinals, including Gregory X, Urban V and Urban VI. Urban IV was the son of a cobbler of Troyes, France. He studied theology and common law in Paris and was appointed a canon of Laon and later Archdeacon of Liège. At the First Council of Lyon (1245)