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.
Roman emperor
The Tetrarchy ultimately degenerated into civil war, but the eventual victor, Constantine the Great, restored Diocletian's division of Empire into East and West. He kept the East for himself and founded his city of Constantinople as its new capital. Constantine's own dynasty was also soon swallowed up in civil war and court intrigue until it was replaced, briefly, by Julian the Apostate's general Jovian and then, more permanently, by Valentinian I and the dynasty he founded in 364. Though a soldier from a low middle-class background, Valentinian was made emperor by a conclave of senior generals and civil officials.