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 I Pope Urban I Pope Urban I () was Bishop of Rome or Pope from 222 to 23 May 230. He was born in Rome and succeeded Pope Callixtus I, who had been martyred. It was previously believed for centuries that Urban I was also martyred. However, recent historical discoveries now lead scholars to believe that he died of natural causes. Much of Urban's life is shrouded in mystery, leading to many myths and misconceptions. Despite the lack of sources he is the first Pope whose reign can be definitely dated. Two prominent sources do exist for Urban's pontificate: Eusebius' history