Constantinople
Constantinople (; ) was the capital city of the Roman/Byzantine Empire (330–1204 and 1261–1453), and also of the brief Crusader state known as the Latin Empire (1204–1261), until finally falling to the Ottoman Empire (1453–1923). It was reinaugurated in 324 from ancient Byzantium as the new capital of the Roman Empire by Emperor Constantine the Great, after whom it was named, and dedicated on 11 May 330. The city was located in what is now the European side and the core of modern Istanbul.
Papal primacy
The event that is often considered to have been the first conflict between Rome and Constantinople was triggered by the elevation of the see of Constantinople to a position of honour, second only to Rome on the grounds that, as capital of the eastern Roman empire, it was now the "New Rome". This was promulgated in the First Council of Constantinople (381) canon 3 which decreed: "The Bishop of Constantinople, however, shall have the prerogative of honour after the Bishop of Rome because Constantinople is New Rome." It has been asserted by many that the Council of Rome, a synod held by Pope Damasus I in the following year, 382, protested against this raising of the bishop of the new imperial capital, just fifty years old, to a status higher than that of the bishops of Alexandria and Antioch, and stated that the primacy of the Roman see was established by no gathering of bishops but by Christ himself. Thomas Shahan says that, according to Photius too, Pope Damasus approved the council of Constantinople, but he adds that, if any part of the council were approved by this pope, it could have been only its revision of the Nicene Creed, as was the case also when Gregory the Great recognized it as one of the four general councils, but only in its dogmatic utterances. In Catholic doctrine, no council, regardless of who summoned it or who presided over it, is ecumenical unless it is confirmed or at least recognized as such by the pope.