A soldier's son
Flavius Valerius Constantinus was born on 27 February in about 272 at Naissus, now Niš in Serbia, the son of an army officer, Constantius, and of Helena, a woman of humble birth — an inn servant, said Ambrose. In 293 Diocletian made Constantius one of the four rulers of his Tetrarchy, Caesar of the west, and Constantius put Helena aside for a Tetrarch's daughter. Constantine grew up at Diocletian's court in Nicomedia, half apprentice and half hostage, and served under Galerius on the Danube and in Persia.
When Diocletian abdicated in 305 the young man was passed over. He slipped away to join his father, crossed with him to Britain, and when Constantius died at York on 25 July 306 the army proclaimed the son Augustus on the spot. Galerius grudgingly allowed him the lesser title of Caesar. The system of four rulers, held together by Diocletian alone, began to come apart.
The bridge and the cross
By 312 four men claimed the purple. Constantine crossed the Alps with perhaps 40,000 men against Maxentius, who held Rome, and took Turin and Verona. On 28 October 312 Maxentius came out to fight with the Tiber at his back; his army was pushed into the river at the Milvian Bridge and he drowned. Constantine entered Rome the next day. Lactantius says a dream the night before told him to mark his soldiers' shields with a sign of Christ. Eusebius, writing after Constantine's death, gives a grander story.
“By this conquer.”
In 313 he and Licinius, ruler of the east, agreed at Milan to give Christians and everyone else freedom of worship and to return the Church's confiscated property. In 324 he beat Licinius too and ruled the whole empire alone.
One empire, one Church
A Christian emperor found the Church at war with itself. In 325 he summoned the bishops to Nicaea, sat among them, and pressed them to accept a creed that declared the Son “of one substance” with the Father — the first ecumenical council and the origin of the Nicene Creed. He built churches at his own expense in Rome, Jerusalem and his new capital, exempted clergy from taxes, made Sunday a rest day and let bishops judge civil cases. He also kept the title pontifex maximus and put the sun god on his coins for years.
The same emperor had his eldest son Crispus put to death in 326, and his wife Fausta soon after; no ancient writer gives an agreed reason. On 11 May 330 he dedicated Constantinople on the site of Byzantium as a second Rome, and the gold solidus he introduced kept its weight for seven centuries.
Death and the long shadow
Falling ill in the spring of 337, Constantine at last asked for baptism, from Eusebius, bishop of Nicomedia, and died on 22 May near that city wearing the white robe of the newly baptised. He was buried in Constantinople in the Church of the Holy Apostles, which he had built with twelve cenotaphs around his own tomb. His three surviving sons divided the empire after the army had murdered most of his other male relatives.
He did not make the empire Christian; that took another half-century. But he made Christianity the religion of the emperor, gave it wealth and law and a council, and founded the city that carried Roman rule to 1453. The Eastern Church calls him a saint and “equal to the apostles”; the West called him “the Great” and, for centuries, believed a forged deed by which he gave the pope the western empire.