From Persecution to Empire: Paul, Constantine and Nicaea

Christianity spread quickly through the Roman Empire, aided by Roman roads, the common Greek language and the missionary journeys of Paul, who argued that non-Jews could join without adopting Jewish law. This decision helped turn a Jewish movement into a separate religion with a largely Gentile membership. Romans often viewed Christians with suspicion for refusing to worship the emperor and traditional gods, and persecution occurred at intervals, most severely under Diocletian from 303.

Everything changed with Constantine, who attributed his victory at the Milvian Bridge in 312 to the Christian God; the Edict of Milan (313) granted toleration, and in 325 he summoned the Council of Nicaea to settle disputes over Christ's divinity. In 380, under Theodosius I, Nicene Christianity became the empire's official religion. Historians debate whether this alliance with power strengthened the church or compromised it, and how sincere Constantine's conversion was.