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 Ravenna who held Rome as the antipope "Clement III". Gregory had repeatedly clashed with the emperor Henry IV over papal authority. Despite the Walk to Canossa, Gregory had backed the rebel Duke of Swabia and again excommunicated the emperor. Henry finally took Rome in 1084 and installed Clement III in his place. Urban took up the policies of Pope Gregory VII and, while pursuing them with determination, showed greater flexibility and diplomatic finesse. Usually kept away from Rome, Urban toured northern Italy and France. A series of well-attended synods held in Rome, Amalfi, Benevento, and Troia supported him in renewed