Constantine I, known as Constantine the Great, properly Flavius Valerius Aurelius Constantinus c.274-337AD
Roman emperor

Constantine was born in Naissus, in Upper Moesia, the eldest son of Constantius Chlorus and Helena. He first distinguished himself as a soldier in Diocletian's Egyptian expedition (296), next under Galerius in the Persian war. In 305 the two emperors Diocletian and Maximian abdicated, and were succeeded by Constantius Chlorus and Galerius. Constantine joined his father, who ruled in the West, on the expedition against the Picts at Boulogne, and before Constantius died at York (306) he designated his son as his successor; the army proclaimed him Augustus. Galerius did not dare to quarrel with Constantine, yet he granted him the title of Caesar only, refusing that of Augustus. Political complications now increased, until in 308 there were actually no fewer than six emperors at once - Galerius, Licinius and Maximian in the East; and Maximian, Maxentius his son, and Constantine in the West. Maxentius drove his father from Rome, and after some intrigues, Maximian committed suicide (309). Maxentius threatened Gaul with a large army. Constantine, crossing the Alps by Mont C�nis, defeated Maxentius on three occasions; Maxentius was drowned after the last great victory at the Milvian Bridge near Rome (312).

Before the battle a flaming cross inscribed 'In this conquer' was said to have caused Constantine's conversion to Christianity; and the edict of Milan (313), issued conjointly with Licinius, gave civil rights and toleration to Christians throughout the empire. Constantine was now sole emperor of the West; and with the death of Galerius in 311 and of Maximian in 313, Licinius became sole emperor of the East. After a war (314) between the two rulers, Licinius was forced to cede Illyricum, Pannonia and Greece; and for the next nine years Constantine devoted himself vigorously to the correction of abuses and the strengthening of his frontiers. In 323 Constantine again defeated Licinius, and put him to death; he was now sole ruler of the Roman world. He chose Byzantium (modern day Istanbul) for his capital, and in 330 inaugurated it under the name of Constantinople ('City of Constantine').

Christianity became a state religion in 324, although paganism was not suppressed. In 325 the great Church Council of Nicaea was held, in which the court sided against the Arians and the Nicene Creed was adopted. Yet it was only shortly before his death that Constantine was baptised. The story of his baptism at Rome by Pope Sylvester I (pope 314-335) in 326, and of the so-called Donation of Constantine, long treated as an argument for the temporal power of the papacy, is unhistorical. His later years were vicious, seeing the execution of his eldest son Crispus (326) for treason and of his own second wife Fausta (327) on some similar charge. He proposed to divide the empire between his three sons by Fausta - Constantius, Constantine II and Constans I - but in 340 Constantine II lost his life in war with Constans.

Bibliography: Joseph Burkhardt, The Age of Constantine the Great (1983, trans by Moses Hadas); Ramsay MacMullen, Constantine (1969); Norman H Baynes, Constantine the Great and the Christian Church (1929), Eusebius of Caesarea, Constantine.