Christianity in Turkey
Constantinople became established in the ecclesiastical hierarchy at the Council of Constantinople in 381. Second only to Rome, the legendary origins of the Patriarchate of Constantinople go back to St. Andrew, Metrophanes and Alexander of Constantinople. Constantinople's primacy over the Patriarchates of Alexandria and Antioch was reaffirmed at the Council of Chalcedon in 481, after which the papacy in Rome supported Constantinople in its dispute with Alexandria over monophysitism. Later, when Rome sought to assert its primacy over Byzantium, the Eastern Orthodox church developed the doctrine of pentarchy as a response.
Ecumenical Patriarch of Constantinople
The (arch)bishopric of Constantinople has had a continuous history since the founding of the city in 330 AD by Constantine the Great. After Constantine the Great had enlarged Byzantium to make it into a second capital city in 330, it was thought appropriate that its bishop, once a suffragan of the Exarch of Thrace and Macedonia, the Metropolitan of Heraclea, should be elevated to an archbishopric. For many decades the heads of the church of Rome opposed this ambition, not because anyone thought of disputing their first place, but because they defended the 'Petrine principle' by which all Patriarchates were derived from Saint Peter and were unwilling to violate the old order of the hierarchy for political reasons.
In 381, the First Council of Constantinople declared that "The Bishop of Constantinople shall have the primacy of honour after the Bishop of Rome, because it is New Rome" (canon iii). The prestige of the office continued to grow not only because of the obvious patronage of the Byzantine Emperor but because of its overwhelming geographical importance.