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 Ottoman Empire
The Ottoman conquest of Constantinople in 1453 by Mehmed II cemented the status of the Empire as the preeminent power in southeastern Europe and the eastern Mediterranean. After taking Constantinople, Mehmed met with the Orthodox patriarch, Gennadios and worked out an arrangement in which the Orthodox Church, in exchange for being able to maintain its autonomy and land, accepted Ottoman authority. Because of bad relations between the latter Byzantine Empire and the states of western Europe as epitomized by Loukas Notaras's famous remark "Better the Sultan's turban than the Cardinal's Hat", the majority of the Orthodox population accepted Ottoman rule as preferable to Venetian rule.