During the reign of Constantine the Great, Christianity received official permission to exist and develop. The first decree favoring Christianity was issued in 311 by Galerius, who had been one of its most ferocious persecutors.
This decree gave pardon to the Christians for their former stubborn resistance to government orders aimed at turning them back to paganism, and announced their legal right to exist. It declared: Christians may exist again, and may establish their meetings, yet so that they do nothing contrary to good order. Wherefore, in accordance with this indulgence of ours, they will be bound to pray their God for our good estate, that of the commonwealth, and their own.
Two years later, after his victory over Maxentius and agreement with Licinius, Constantine met Licinius in Milan, where they issued the very interesting document incorrectly called the Edict of Milan. The original text of this document has not been preserved, but a Latin manuscript of Licinius sent to the prefect of Nikomedia has been preserved by Lactantius. A Greek translation of the Latin original is given by Eusebius in his Ecclesiastical History.