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 declarations against simony, lay investitures, clerical marriages (partly via the "cullagium" tax), and the emperor and his antipope. He facilitated the marriage of Matilda, countess of Tuscany, with Welf II, duke of Bavaria. He supported the rebellion of Prince Conrad against his father and bestowed the office of groom on Conrad at Cremona in 1095. While there, he helped arrange the marriage between Conrad and Maximilla, the daughter of Count Roger of Sicily, which occurred later that year at Pisa; her large dowry helped finance Conrad's continued campaigns. The Empress Adelaide was encouraged in her charges of sexual coercion against