Pope Innocent III

Lotario de' Conti di Segni became Pope Innocent III on 8 January 1198, at thirty-seven. He spent the next eighteen years asserting that no king in Christendom stood above him, using interdict and excommunication as levers - with mixed success. His decretals and the Fourth Lateran Council sharpened Western canon law into something enforceable. He launched crusades against Muslims in Iberia, pagans in Livonia, and Cathars in southern France. The Fourth Crusade, which he organized in 1202, veered off course: his army sacked Constantinople in 1204 despite his explicit orders, and though he excommunicated them for it, he later accepted the outcome as divine will to reunite the churches. It did the opposite - the brutality deepened the schism, and Byzantium, when restored in 1261, never recovered its strength. He died 16 July 1216.