When did Constantine became Emperor of Rome?
Constantine I became Emperor in the “Gallic Prefecture” of Britain, Gaul and the Iberian Peninsula, on the death of his father in 306. In 312 he defeated Maxentius at the Milvian Britdge (at which point he openly embraced Christianity) and thus became sole Emperor in the West. A rival, Licinius, ruled the Eastern half until 324, when Constantine defeated him in civil war. Constantine then ruled the whole empire until his death in 337.