Roman emperor Constantine the Great (c. 275–337) is credited with no less than beginning a new era in history. His father, Constantius, was ruler of the Roman Empire when he died in 306. Though Constantine was named emperor by Roman soldiers, a power struggle ensued. During a battle near Rome in 312, Constantine, who had always been sympathetic toward Christians, reportedly saw a vision of a flaming cross. He emerged from the conflict both converted and victorious. For the next 12 years, Constantine ruled the West Roman Empire while Licinius (also tolerant to Christians) ruled the East. But a struggle between the two emperors ended in death for Licinius and, beginning in 325, Constantine ruled as sole emperor.

During Constantine’s reign, Christians regained freedom of worship and the Christian Church became legal. In 325 he convened the Council of Nicaea (from whence came the Nicene Creed so familiar to Christians today). In moving the capital of the Roman Empire to Byzantium (in 330), Constantine shifted the empire’s focus from west to east and in so doing laid the foundation for the Byzantine Empire. The Eastern Orthodox Church regards Constantine as a saint.