Early Christianity and Byzantine period Christianity spread to
Nicomedia during the middle of the 1st century, while the city became the oldest bishopric established in the region of
Bithynia, in northwestern
Asia Minor. According to the Christian tradition, the first bishop was
Prochorus, one of the
Seven Deacons. Nicomedia became a significant important administrative center during the reign of Emperor
Diocletian. The latter aimed at transforming the city into a new capital of the
Roman Empire. In 303, during the reign of the same emperor, the Christians of Nicomedia witnessed persecution, while another wave of persecution against the Christians occurred in 324 under
Licinius. The number of the local Christian victims has not been estimated but it is believed that they were thousands. Among the martyrs were the legionaries
Dorotheus,
Gorgonius,
Panteleemon and
George, as well as the local bishop
Anthimus. In 337 bishop
Eusebius of Nicomedia baptised Emperor
Constantine the Great on his deathbed. At 451, the local bishopric was promoted to a
metropolitan see under the jurisdiction of the
Ecumenical Patriarchate of Constantinople. The metropolis of Nicomedia was ranked 7th in the
Notitiae Episcopatuum among the metropolises of the Patriarchate. The last attested metropolitan of the 14th century was Maximos (1324–1327). After 1327 the metropolitan see remained vacant until 1356, most likely due to the
prolonged Ottoman siege of the city. Nicomedia was the last city of Bithynia that remained under Byzantine control, until it finally fell in 1337. After the
Fall of Constantinople, the Ottomans led to the incorporation of the Patriarchate of Constantinople into the Ottoman
millet system and to subsequent reforms in the ecclesiastical administration. As a result, the church of Nicomedia was restored to its former status. ==Geography and demographics==