The Edict of Milan (313 CE) declared that the Roman Empire would be neutral with regard to religious worship, officially ending all government-sanctioned persecution especially of Christianity. The Edict was issued in the names of the Western tetrarch Constantine the Great, and Licinius, the Eastern tetrarch.

Enforcement of the Edict returned the meeting places and other properties which had been confiscated from the Christians and sold out of the government treasury: " ... the same shall be restored to the Christians without payment or any claim of recompense and without any kind of fraud or deception ... ". It gave to Christianity (and any other religion) a status of legitimacy alongside of paganism, and in effect disestablished paganism as the official religion of the Roman Empire and its armies.

In the attempt to consolidate the entire Roman Empire under one ruler, Licinius soon marched against Constantine. As part of his effort to win the loyalty of the army, Licinius exempted the army and civil service from the Edict's policy of toleration, allowing him to expel the Christians. Some Christians consequently lost property and at least a few lost their lives. A legend survives, for example, relating how, around 320 CE, forty Christians in Sevaste refused to pour out a drink-offering in tribute to the pagan gods; as punishment, they were beaten and jailed. When they still refused to participate in the rite, they were made to stand naked on ice in mid-winter until they froze to death. A handful of them decided to renounce Christianity and joined the other soldiers by the warm fires, while an equal number decided to confess their heretofore hidden Christianity and join those on the ice. The tradition also tells of angels descending, to place crowns on the martyrs' heads.

In the end, sometime in 324 CE, Constantine gained sole possession of the Empire, and ordered Licinius executed for treason.