Early Christian and Byzantine period

Early Christian and Byzantine period
Main articles: Early Christianity and Byzantine Anatolia
See also: Successors of the Byzantine Empire and States in late medieval Anatolia

Originally a church, then a mosque, later a museum, and now a mosque again, the Hagia Sophia in Istanbul was built by the Byzantine emperor Justinian I in 532–537 AD.[51]
According to Acts of Apostles 11,[52] Antioch (now Antakya), a city in southern Turkey, is the birthplace of the first Christian community.[53]

In 324, Constantine I chose Byzantium to be the new capital of the Roman Empire, renaming it New Rome. Following the death of Theodosius I in 395 and the permanent division of the Roman Empire between his two sons, the city, which would popularly come to be known as Constantinople, became the capital of the Eastern Roman Empire. This empire, which would later be branded by historians as the Byzantine Empire, ruled most of the territory of present-day Turkey until the Late Middle Ages;[54] although the eastern regions remained firmly in Sasanian hands up to the first half of the seventh century. The frequent Byzantine-Sassanid Wars, as part of the centuries long-lasting Roman-Persian Wars, fought between the neighbouring rivalling Byzantines and Sasanians, took place in various parts of present-day Turkey and decided much of the latter’s[clarification needed] history from the fourth century up to the first half of the seventh century.

Several ecumenical councils of the early Church were held in cities located in present-day Turkey including the First Council of Nicaea (Iznik) in 325, the First Council of Constantinople (Istanbul) in 381, the Council of Ephesus in 431, and the Council of Chalcedon (Kadıköy) in 451.[55]