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
Gerard (archbishop of York) archdeacon of Rouen. He served in the royal chancery under successive kings of England, William I and William II. Gerard was appointed Lord Chancellor of England in 1085, and was present at William I's deathbed in 1087. He continued as Chancellor to William Rufus until 1092; what precipitated his loss of office is unclear. He retained the king's trust, for Rufus employed him in 1095 along with William Warelwast on a diplomatic mission to Pope Urban II regarding Archbishop Anselm receiving the pallium, the sign of an archbishop's authority. Rufus offered to recognise Urban as pope rather than the Antipope