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.
History of Europe
When Emperor Constantine had reconquered Rome under the banner of the cross in 312, he soon afterwards issued the Edict of Milan in 313 (preceded by the Edict of Serdica in 311), declaring the legality of Christianity in the Roman Empire. In addition, Constantine officially shifted the capital of the Roman Empire from Rome to the Greek town of Byzantium, which he renamed Nova Roma – it was later named Constantinople ("City of Constantine").