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 Lucius II Pope of his temporal power. The principal groups involved in this movement were the merchants and artisans, while the urban nobility kept their neutrality. The Senate, which practically took all temporal power from the Pope during the pontificate of Innocent II, had been managed with considerable skill and firmness by Lucius at the beginning of his pontificate, convincing many senators to either leave the Capitoline Hill or to lay down their magisterium. Now, encouraged by Lucius II's defeat, the Senate, led by Giordano Pierleoni, brother of the former Antipope Anacletus II, rebelled against Lucius II, driving out the papal prefects