Eastern Church ( Eastern Orthodox Church) and Western Church (Roman Catholic Church). In 1053, the first step was taken in the process which led to formal schism. The Patriarch of Constantinople ordered the closure of all Eastern Churches in the city. The patriarch's purpose in closing the Latin churches was "to cut short any attempt at conciliation".
In 1054, the Papal legate traveled to Constantinople for purposes that included refusing to Cerularius the title of "Ecumenical Patriarch" and insisting that he recognize Rome's claim to be the head and mother of the churches. The papal legation was to seek help from the Byzantine Emperor in view of the Norman conquest of southern Italy and to deal with recent attacks by Leo of Ohrid against the use of unleavened bread and other Western customs, attacks that had the support of Cerularius (Michael Caerularius); Axel Bayer says the legation was sent in response to two letters, one from the Emperor seeking assistance in arranging a common military campaign by the eastern and western empires against the Normans, and the other from Cerularius. On the refusal of Cerularius, the leader of the legation, Cardinal Humbert, excommunicated him, and in return Cerularius excommunicated Cardinal Humbert and the other legates. This was only the first act in a centuries-long process that eventually became a complete schism.
Since Pope Leo had died and Cerularius' excommunication applied only to the legates personally, still, the Church split along doctrinal, theological, linguistic, political, and geographical lines, and the fundamental breach has never been healed. Each side sometimes accused the other of having fallen into heresy and of having initiated the division. The Crusades, the Massacre of the Latins in 1182, the West's retaliation in the Sacking of Thessalonica in 1185, the capture and sack of Constantinople in 1204, and the imposition of Latin patriarchs made reconciliation more difficult. Establishing Latin hierarchies in the Crusader states meant that there were two rival claimants to each of the patriarchal sees of Antioch, Constantinople, and Jerusalem, making the existence of schism clear.
In 1054, the Papal legate traveled to Constantinople for purposes that included refusing to Cerularius the title of "Ecumenical Patriarch" and insisting that he recognize Rome's claim to be the head and mother of the churches. The papal legation was to seek help from the Byzantine Emperor in view of the Norman conquest of southern Italy and to deal with recent attacks by Leo of Ohrid against the use of unleavened bread and other Western customs, attacks that had the support of Cerularius (Michael Caerularius); Axel Bayer says the legation was sent in response to two letters, one from the Emperor seeking assistance in arranging a common military campaign by the eastern and western empires against the Normans, and the other from Cerularius. On the refusal of Cerularius, the leader of the legation, Cardinal Humbert, excommunicated him, and in return Cerularius excommunicated Cardinal Humbert and the other legates. This was only the first act in a centuries-long process that eventually became a complete schism.
Since Pope Leo had died and Cerularius' excommunication applied only to the legates personally, still, the Church split along doctrinal, theological, linguistic, political, and geographical lines, and the fundamental breach has never been healed. Each side sometimes accused the other of having fallen into heresy and of having initiated the division. The Crusades, the Massacre of the Latins in 1182, the West's retaliation in the Sacking of Thessalonica in 1185, the capture and sack of Constantinople in 1204, and the imposition of Latin patriarchs made reconciliation more difficult. Establishing Latin hierarchies in the Crusader states meant that there were two rival claimants to each of the patriarchal sees of Antioch, Constantinople, and Jerusalem, making the existence of schism clear.