Pope Leo IX

1051 charter of Leo IX

Leo IX favored celibacy for clergy in his reformation of the Catholic Church. One of his first public acts was to hold the well-known Easter synod of 1049, at which celibacy of the clergy (down to the rank of subdeacon) was required anew. Also, the Easter synod was where the pope at least succeeded in making clear his own convictions against every kind of simony. The greater part of the year that followed was occupied in one of those progresses through Italy, Germany and France which form a marked feature in Leo IX's pontificate. After presiding over a synod at Pavia, he joined Henry III in Saxony and accompanied him to Cologne and Aachen. He also summoned a meeting of the higher clergy in Reims in which several important reforming decrees were passed. At Mainz he held a council at which the Italian and French as well as the German clergy were represented, and ambassadors of the Byzantine emperor were present. Here too, simony and the marriage of the clergy were the principal matters dealt with.

After his return to Rome, Leo held another Easter synod on 29 April 1050. It was occupied largely with the controversy about the teachings of Berengar of Tours. In the same year he presided over provincial synods at Salerno, Siponto and Vercelli, and in September revisited his native Germany, returning to Rome in time for a third Easter synod, at which the question of the reordination of those who had been ordained by simonists was considered. In 1052 he joined the emperor at Pressburg and vainly sought to secure the submission of the Hungarians. At Regensburg, Bamberg and Worms, the papal presence was celebrated with various ecclesiastical solemnities. In early 1053, Leo arbitrated a dispute between the archbishop of Carthage and the bishop of Gummi-Mahdia over ecclesiastical precedence.[7]

Patriarch Michael I Cerularius of Constantinople, through Leo of Ohrid, Archbishop of Bulgaria, wrote to the pope denouncing the use of unleavened bread and fasting days in the Latin church. and afterwards closed down the Latin rite churches of Constantinople and stopped remembrance for the pope in the diptychs and wrote letters to the other patriarchs against the pope. He was denounced by the patriarch of Antioch, Peter III, for trying to incite schism within the church. Leo IX sent a letter to Michael I in 1054, citing a large portion of the Donation of Constantine, believing it genuine.[8]

Leo assured Michael that the donation was completely genuine, not a fable, so only the apostolic successor to Peter possessed that primacy and was the rightful head of all the Church. Before his death, Leo IX had sent a legatine mission under Cardinal Humbert of Silva Candida to Constantinople to negotiate with Patriarch Michael Cærularius in response to his actions concerning the church in Constantinople.[9] Humbert quickly disposed of negotiations by delivering a bull excommunicating the Patriarch.[5] This act, although legally invalid due to the pope's death at the time, was answered by the patriarch's own bull of excommunication against Humbert and his associates and is popularly considered the official split between the Eastern and Western Churches. The patriarch rejected the claims of papal primacy, and subsequently the Church was split in two in the Great East–West Schism of 1054.

In constant fear of attack from the Normans in the south of Italy, the Byzantines turned in desperation to the Normans' own spiritual chief, Pope Leo IX, and, according to William of Apulia, begged him "to liberate Italy that now lacks its freedom and to force that wicked people, who are pressing Apulia under their yoke, to leave." After a fourth Easter synod in 1053, Leo IX set out against the Normans in the south with an army of Italians and Swabian mercenaries. "As fervent Christians the Normans were reluctant to fight their spiritual leader and tried to sue for peace but the Swabians mocked them – battle was inevitable."[10] Leo IX led the army himself, but his forces suffered total defeat at the Battle of Civitate on 15 June 1053.[11] Nonetheless, on going out from the city to meet the victorious enemy he was received with every token of submission, pleas for forgiveness and oaths of fidelity and homage. From June 1053 to March 1054 the pope was nevertheless held hostage at Benevento, in honourable captivity, until he acknowledged the Normans conquests in Calabria and Apulia. He did not long survive his return to Rome, where he died on 19 April 1054.