Constantine I, also known as Constantine the Great, was Roman emperor from 306 to 337 AD, and the first to convert to Christianity. Born in Naissus, Dacia Mediterranea, he was the son of Flavius Constantius, a Roman army officer of Illyrian origin who had been one of the four rulers of the Tetrarchy. His mother, Helena, was a Greek and a Christian, and of low birth. Constantine served with distinction under the Roman emperors Diocletian and Galerius. He began his career by campaigning in the eastern provinces before being recalled in the west to fight alongside his father in Britain. After his father's death in 306, Constantine became emperor. He was acclaimed by his army at Eboracum, and eventually emerged victorious in the civil wars against emperors Maxentius and Licinius to become the sole ruler of the Roman Empire by 324.