Constantine was brought up at the court of Diocletian. After a series of civil wars Constantine became first western emperor (by his time the empire was ruled by two co-emperors) and then sole emperor (324). He ascribed his success to a vision of a Christian cross and began favourable treatment of Christians.

As the Christian church grew in power disputes arose. The dispute over the question of Trinity threatened to split the church.

Constantine called a council of churchmen at Nicaea in Asia Minor in 325. The Nicene creed came out of this council. Constantine was baptized shortly before his death.