How a bishop under Heraclea became first among Orthodox equals
Before 330 AD, the bishop of Byzantium answered to a senior bishop in nearby Heraclea. Then Constantine moved his residence to the city and renamed it New Rome, and its church rose with it. Within a few generations its patriarch ranked second only to the pope, and later claimed equal privileges.
Proximity to the emperor was the secret. Bishops travelling to the capital to seek imperial help passed through the patriarch, who became a natural go-between, and a standing council of visiting bishops, the resident synod, began dealing with questions affecting the whole Church. In 381 the First Council of Constantinople gave its bishop primacy of honour after Rome's, explicitly because the city was the New Rome. At Chalcedon in 451, Canon 28 went further, granting equal privileges with Rome and placing Pontus, Asia and Thrace under Constantinople's authority.
For nearly a millennium the patriarch presided over the Byzantine church from Hagia Sophia, and the see became known as the Great Church of Christ. Its missions shaped Eastern Europe. In the 860s Cyril and Methodius, with Constantinople's approval, went to Great Moravia, devised the Glagolitic script and translated liturgy into Old Church Slavonic so Slavs could worship in a language they understood. Bulgaria under Boris I accepted Christianity in 864, Vladimir of Kiev was baptised in 988, and in 1219 Constantinople recognised the independent Serbian church founded by Saint Sava.
The famous rupture with Rome grew out of a dispute that at first seemed manageable. In 1053 Patriarch Michael Cerularius had a letter sent criticising Western customs, notably unleavened Eucharistic bread, as well as papal claims and the Filioque addition to the creed. Papal legates led by Humbert arrived in April 1054, met a cold reception and issued a bull excommunicating Cerularius and his supporters. Its legal force is questioned, since Pope Leo IX had already died, but the episode is conventionally treated as the start of the East–West Schism, which hardened only gradually.
Today the Ecumenical Patriarch is one head among the autocephalous Orthodox churches, honoured as first among equals rather than ruling over them. Tradition grants the see some special prerogatives, such as hearing appeals when invited and founding monasteries under its direct authority in other territories, though not every Orthodox church accepts all of them.
Source: Ecumenical Patriarchate of Constantinople
