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
Counts of Clermont-Tonnerre Counts of Clermont-Tonnerre Clermont-Tonnerre is the name of a French noble family, members of which played some part in the history of France, especially in Dauphiné, from about 1100 to the French Revolution (1789–99). Sibaud, lord of Clermont in Viennois, who first appears in 1080, was the founder of the family. His descendant, another Sibaud, commanded some troops which aided Pope Calixtus II in his struggle with the Antipope Gregory VIII. In return for this service, it is said that the pope allowed him to add certain emblems, two keys and a tiara to the arms of his family. A