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 the Byzantine Empire
This history of the Byzantine Empire covers the history of the Eastern Roman Empire from late antiquity until the Fall of Constantinople in 1453 AD. Several events from the 4th to 6th centuries mark the transitional period during which the Roman Empire's east and west divided. In 285, the emperor Diocletian (r. 284–305) partitioned the Roman Empire's administration into eastern and western halves. Between 324 and 330, Constantine I (r. 306–337) transferred the main capital from Rome to Byzantium, later known as "Constantinople" ("City of Constantine") and "Nova Roma" ("New Rome"). Under Theodosius I (r. 379–395), Christianity became the Empire's official state religion and others such as Roman polytheism were proscribed. And finally, under the reign of Heraclius (r. 610–641), the Empire's military and administration were restructured and adopted Greek for official use instead of Latin. Thus, although it continued the Roman state and maintained Roman state traditions, modern historians distinguish Byzantium from ancient Rome insofar as it was oriented towards Greek rather than Latin culture, and characterised by Orthodox Christianity rather than Roman polytheism.