Byzantium Timeline
4th Century

Byzantium Timeline (301-400 A.D.)




Constantine I becomes sole Roman Emperor

A period of civil war concludes with Constantine I as sole emperor of the eastern and western Roman Empire. He commences construction of New Rome (Constantinople) on the site of the old Greek city of Byzantium.

Constantine instigates a series of legislative changes that favour Christians within the Roman Empire.


The Council of Nicaea

Constantine is not prepared to tolerate divisions within the Christian Church, a threat to Roman stability that he regards as "formidable as any war or battle". An ecumenical ("world –wide") council of church leaders is convened at Nicaea to debate Arianism; a popular religious doctrine, which holds that Jesus Christ ("the Son"), is inferior to God ("the Father").

The Council counters Arianism with the Nicene Creed, a theological formulation which includes the statement that the Son and Father are of the same substance and therefore equal. Although the Council apparently 'solves' the problem of Arianism, the heresy continues to exist and gain many adherents over the next two centuries, including some of Constantine’s successors


Constantinople formally dedicated as Roman Capital

330 is often treated as a convenient starting point for referring to the Roman Empire in the East as the "Byzantine Empire" or "Byzantium".