This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
In February 313 CE, the co-emperors Constantine and Licinius met at Mediolanum, modern Milan, and agreed to extend legal toleration to Christianity throughout the Roman Empire, along with restoring property that had been confiscated during the persecutions that preceded their agreement. No original inscribed text of the edict survives; its substance is known only through later writers, chiefly Lactantius and Eusebius, whose Greek text in the Ecclesiastical History differs in detail from Lactantius's own Latin version of the same agreement.
What the agreement accomplished was narrower than its later reputation suggests. It ended Christian persecution as settled state policy across the whole empire, closing the era of legal repression that had run, with interruptions, since the faith's earliest centuries. It did not, on its own, make Christianity the empire's official or exclusive religion, a distinction worth keeping separate from the Edict of Thessalonica, issued sixty seven years later, which went considerably further.
What this changed for Christianity's spread was the removal, at a stroke, of the legal risk that had shadowed the faith's growth across the empire for two and a half centuries: Christians could now worship, hold property and organize openly under imperial law, a change in status that made every later step toward Christianity becoming Rome's dominant religion possible.