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.
Fall of Constantinople
With the capture of Constantinople, Mehmed II had acquired the "natural" capital of its kingdom, albeit one in decline due to years of war. The loss of the city was a crippling blow to Christendom, and it exposed the Christian west to a vigorous and aggressive foe in the east. The Christian re-conquest of Constantinople remained a goal in Western Europe for many years after its fall to the House of Osman. Rumors of Constantine XI's survival and subsequent rescue by an angel led many to hope that the city would one day return to Christian hands. Pope Nicholas V called for an immediate counter-attack in the form of a crusade. When no European monarch was willing to lead the crusade, the Pope himself decided to go, but his early death stopped this plan. As Western Europe entered the 16th century, the age of Crusading began to come to an end.