13th and 14th ecumenical councils of the Roman Catholic Church.
The First Council of Lyon was convened by Pope Innocent IV in 1245 after he fled to Lyon from the besieged city of Rome; the pope deposed the emperor, Frederick II , and urged support for Louis IX on the Seventh Crusade . At the Second Council in 1274, Pope Gregory X nominally reunited the Eastern and Western churches, but the Greek clergy soon repudiated the union.