Called the Great, born in Moesia, son of Constantius Chlorus by Helena; on the death of his father at York, where he accompanied him, was proclaimed Emperor by the troops; this title being challenged by Maximian, his father-in-law, and Maxentius, his brother-in-law, he took up arms against first the one and then the other, and defeated them; when one day he saw a cross in the sky with the words By this Conquer in Greek, under this sign, known as the labarum, which he adopted as his standard, he accordingly marched straight to Rome, where he was acknowledged Emperor by the Senate in 312; and thereafter an edict was issued named of Milan, granting toleration to the Christians; he had still to extend his empire over the East, and having done so by the removal of Lucinius, he transferred the seat of his empire to Byzantium, which hence got the name of Constantinople, i. e. Constantine's city; had himself baptized in 337 as a Christian, after having three years before proclaimed Christianity the State religion (274-337).