In New Testament times, Greek culture was predominant in the eastern regions of the Roman Empire. The early growth of the Church, beginning with the missionary activity of St. Paul, eventually led to the Christianization of this Greek civilization.

The Emperor Constantine began a process that led to the adoption of Christianity as the imperial state religion by Emperor Theodosius in the late 4th century. Constantine also moved the empire’s capital from Rome to the small Greek city of Byzantium in 330 and renamed it Constantinople, or New Rome.

Because of Constantinople’s new status as capital of the empire, its church grew in importance. Canon 3 of the First Council of Constantinople (381) stated that the bishop of that city “shall have primacy of honor after the Bishop of Rome because Constantinople is the New Rome.” Thus it assumed a position higher than the more ancient Patriarchates of Alexandria and Antioch. In its disputed 28th Canon, the Council of Chalcedon in 451 recognized an expansion of the boundaries of the Patriarchate of Constantinople and of its authority over bishops of dioceses “among the barbarians,” which has been variously interpreted as referring either to areas outside the Byzantine Empire or to non-Greeks. In any case, for almost a thousand years the Patriarch of Constantinople presided over the church in the eastern Roman (Byzantine) Empire and its missionary activity that brought the Christian faith in its Byzantine form to many peoples north of the imperial borders. The cathedral church of Constantinople, Hagia Sophia (Holy Wisdom), was the center of religious life in the eastern Christian world.

The schism between Rome and Constantinople developed slowly over a long period, and is often described in older books as culminating in 1054 with the mutual excommunications between Patriarch Michael Cerularius and Cardinal Humbert, the papal legate. But for the common people in the Empire, the rift took on real meaning only after the 1204 sacking of Constantinople by the Latins during the Fourth Crusade. As communion with Rome was breaking down, Constantinople began to assume the first position among the churches of the Byzantine tradition.

Constantinople fell to the Ottoman Turks in 1453. While they placed many restrictions on Christians, in some ways the Turks enhanced the Patriarch’s authority by making him the civil leader of the multi-ethnic Orthodox community within the Empire, and he retained his position as the first of the Orthodox Patriarchs. This gave him a certain authority over the Greek Patriarchates of Alexandria, Antioch, and Jerusalem, which were also within Ottoman territory. But the assumption of civil authority carried a heavy price: when the Greeks rebelled against Turkish rule in 1821, the Ottoman sultan held Patriarch Gregory V responsible and had him hanged at the gates of the patriarchal compound. Two metropolitans and 12 bishops followed him to the gallows.

In 1832 an independent Greek state was established, and a separate autocephalous Church of Greece was set up in 1833. After World War I, there was a major exchange of populations between Greece and Turkey. Anti-Greek riots in Istanbul (the new Turkish name for Constantinople) in the 1950s precipitated another exodus of Greeks from Turkey. Now very few remain.