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
Erlembald had to ceded his rights in Milan to Pope Gregory VII. Gregory confirmed Atto and lent his support to Erlembald. At this, the height of his power, an unfortunate fire broke out in the city and was interpreted as divine punishment for supporting the controversial "pataria". The opposition factions in Milan signed a pact against Erlembald. He put down the revolt, but was killed in the battle and buried in S. Celso. From 6 to 26 May in 1095, Pope Urban II was present at Milan for the transferral of the relics of the canonised Erlembald to S. Dionigi. He