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.
Ancient Rome
The West responded with the Crusades, eventually resulting in the Sack of Constantinople by participants of the Fourth Crusade. The conquest of Constantinople in 1204 fragmented what remained of the Empire into successor states; the ultimate victor was the Empire of Nicaea. After the recapture of Constantinople by Imperial forces, the Empire was little more than a Greek state confined to the Aegean coast. The Byzantine Empire collapsed when Mehmed the Conqueror conquered Constantinople on 29 May, 1453.