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
Peace and Truce of God of secular leadership, Robert the Pious (996–1031) espouses an oath that combines both religious movements: The oath is important because it shows that secular powers are now willing to show obedience to ecclesiastical powers and to rein in problematic knights and armies. Furthermore, knightly and martial violence is often subverted by ecclesiastical powers through the use of crusade. For Pope Urban II, at the Council of Clermont in 1095, the subversion of martial violence is effective in dealing with secular violence: The Peace of God and the Truce of God therefore works within the rhetorical landscape of subverting violence by