Saint Leo IX

Saint Leo IX (1002-1054), pope from 1049 to 1054. During his pontificate, in 1054, the long-standing rift between Christians in the Eastern and Western regions of the former Roman Empire culminated in the excommunication by the Western church of the patriarch of Constantinople (see Schism, Great). Leo was born Bruno, son of Count Hugh of Egisheim in Alsace. He was related to Conrad II, Holy Roman emperor, and was elected pope through the influence of Conrad's son and successor, Henry III. Leo pursued the church policy of maintaining celibacy and opposing concubinage and the sale of church offices. He warred against the Normans in southern Italy but was defeated and captured in 1053.

This military venture led directly to the most significant event of his reign: the final breach between the Western church and the Eastern church. Angered by Leo's interference in areas of southern Italy claimed by the Byzantine Empire, the patriarch Michael Cerularius closed all the Latin churches in Constantinople (present-day İstanbul). Leo, who was still in Norman captivity, at first responded with a peremptory letter asserting the primacy of Rome in ecclesiastical affairs. Because a settlement was desired by both sides, however, in January of 1054 Leo dispatched an embassy to Constantinople to negotiate the issue. The negotiations ended on July 16 when Leo's legate, Cardinal Humbert, marched into the church of Hagia Sophia during services and, in full view of the congregation, threw down on the high altar a papal bull excommunicating Cerularius and his supporters. Cerularius responded with counteranathemas a few days later. Leo had meanwhile died (on April 19, 1054), but the events surrounding the mutual excommunication are attributed to his reign because the Roman legates at Constantinople were acting in his name.