Pope Innocent III (1160 or 1161 – 16 July 1216) was Pope from 8 January 1198 until his death. His birth name was Lotario dei Conti di Segni, sometimes anglicised to Lothar of Segni. Pope Innocent was one of the most powerful and influential popes in the history of the papacy. He exerted a wide influence over the Christian regimes of Europe, indeed claiming supremacy over all of Europe's kings. Pope Innocent was central in supporting the Catholic Church's reforms of ecclesiastical affairs through his decretals and the Fourth Lateran Council. This resulted in a considerable refinement of the Western canon law. Pope Innocent is notable for using interdict and other censures to compel princes to obey his decisions, although these measures were not uniformly successful. The pope called for crusades against militant heretics like the Cathars as well as Muslims. One of Pope Innocent's most critical decisions was calling upon Christian forces to begin The Fourth Crusade. Although the Crusades were, in part, originally intended to support the Byzantine Empire at Constantinople from attack by Turkish invaders, the Fourth Crusade resulted in the sack of Constantinople by the Crusaders in 1204, which greatly upset Pope Innocent.