Constantine the Great

Roman emperor from 306 to 337 AD who won a series of civil wars to become sole ruler of the empire, founded Constantinople as a ‘New Rome’ in the East, and steered the empire toward Christianity — decisions historian Anthony Kaldellis treats as the two most consequential of any Roman emperor’s reign.

Constantine rose from within Diocletian’s Tetrarchy, the system of four co-emperors set up to end the Crisis of the Third Century. Passed over for promotion within that system but backed by the armies, he fought his way through a series of rivals — often former allies bound to him by marriage — and emerged as sole emperor in 324 AD after defeating Licinius in the East. Licinius had held a headquarters at Byzantium, on the Bosporus, at the hinge between Europe and Asia; Constantine chose that site to found Constantinople in 330 AD, explicitly conceived as a ‘New Rome’ and the most successful of several such ‘copy-and-paste Romes’ emperors had founded once Rome itself ceased to be their working capital. The city’s population grew from perhaps 20,000–25,000 to half a million within two centuries, driven almost entirely by forced relocation of senatorial households and the extension of Rome’s grain dole to the new capital.

Constantine’s conversion to Christianity, conventionally dated to 312 AD around the Battle of the Milvian Bridge, brought a small, politically marginal faith (perhaps 10% of the population at the time) into direct partnership with the imperial state. Kaldellis reads the conversion as probably sincere rather than cynically convenient — no persuasive account of political payoff survives — while also noting Constantine’s characteristic pragmatism: he continued deploying pre-Christian religious imagery (a colossal statue of himself in the guise of Apollo stood at the centre of Constantinople) even while institutionalising the church.

He was also, by his own contemporaries’ account, ruthless: he had his son Crispus, a popular and competent general, executed without explanation, and followed the execution with the killing of his wife. Sources favourable to Constantine simply stopped mentioning Crispus afterwards. Kaldellis is explicit that Constantine ranks first among Roman emperors not for personal virtue but for the scale and permanence of his decisions — few other rulers, in this telling, ever make choices of comparable, world-historical weight.

In the wiki

• Anthony Kaldellis on the Roman Empire, Byzantium, and the Rise and Fall of Empires — extended discussion of his rise, the founding of Constantinople, and his conversion
• Long Roman Empire — the continuity thesis that treats Constantinople as Rome continuing, not a new state
• Monarchic Republic — the political model his reign inaugurated in its Constantinople-centred form

See also

• Anthony Kaldellis — the historian who discusses him
• Justinian I — the later emperor who, from the same city, recodified Roman law