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
Guilliaume de Montfort Guilliaume de Montfort Guilliaume de Montfort () (died 27 August 1101) was a French bishop, most notably the Bishop of Paris from 1095 to 1101. Montfort's date of birth is not known, but it was some time before the death of his father, Simon I de Montfort in 1087. He was Bishop of Yves some time before becoming the Bishop of Paris. In 1095, Pope Urban II held the Council of Clermont at Clermont-Ferrand, France. It excommunicated Philip I of France and Bertrade de Montfort, William's sister, for adultery. William had been noted as a great supporter of Urban II,