Constantine the Great

Constantine won the empire at the Milvian Bridge (312 CE) under, tradition holds, a sign of the cross. The Edict of Milan (313) ended the persecutions; the Council of Nicaea (325), which he convened and funded, produced the creed that still anchors most of Christianity; and his new capital on the Bosporus — Constantinople — carried Roman Christianity for another eleven centuries.

Constantine's rise ran through the collapse of Diocletian's tetrarchy, the four-ruler system meant to stabilize the empire. On his father Constantius's death at York in 306 the troops proclaimed Constantine, but several rivals stood between him and sole rule. Nearly two decades of maneuver and civil war followed before he governed alone in 324. His personal life carried its own darkness: in 326 he had his eldest son Crispus and his wife Fausta put to death, for reasons the sources only hint at and historians still cannot fully explain.

As a ruler Constantine grafted Christian favor onto Roman practice without abolishing the old order. He funded churches, exempted clergy from public burdens, made Sunday a day of rest, and legislated on manumission and the family in ways the church welcomed, while retaining the title pontifex maximus and much traditional imagery. His governing principle was concord — a single God, a single empire, a single church — and he intervened in doctrinal disputes less as a theologian than as a manager determined that a divided faith should not divide the state.

His power was won on the battlefield. The victory over Maxentius at the Milvian Bridge (312), fought under the sign he said he had been shown, gave him Rome and the West; the defeat of Licinius at Adrianople and Chrysopolis (324) gave him the East and sole rule. He campaigned on the Rhine and Danube against Franks, Alamanni, and Goths, and was preparing an expedition against Persia at his death in 337. The empire he reunified by force he then reorganized around a new Christian capital on the Bosporus.

Historians still debate the sincerity of Constantine's conversion — he was baptized only on his deathbed, kept the pagan title pontifex maximus, and executed his own son and wife. Within church history, his embrace is itself the great debate: did imperial patronage rescue Christianity or capture it? Both cases have been argued for seventeen centuries.

Every established church, and every argument about what establishment costs a faith, descends from Constantine's bargain. The creed of Nicaea remains the most widely recited text in Christendom after the Lord's Prayer.