After his victory at the Milvian Bridge, Constantine was prepared to recognize Licinius as Augustus in the east. The joint meeting at Milan that saw the issue of the Edict of Toleration was followed by a marriage alliance. Licinius married Constantine’s half-sister and each couple had sons whom they agreed to declare Caesars. Dynasticism was back but Constantine was ambitious that his family should prevail over that of his rival. He exploited the differences with Licinius so effectively that war broke out between them. Licinius was allowed to survive a first defeat in 317 but with his territory in the east truncated. This unstable and unsatisfactory arrangement lasted until 324 when Licinius was defeated again (and died a year later) and so Constantine became sole emperor.
Ostensibly the city of Constantinople, the city that would be capital of the Byzantine empire for over a thousand years, was founded to commemorate Constantine’s victory but a powerful motive must have been the need to create a base from which the defence of the empire in the east could be directed. The centuries-old Greek town of Byzantium, on a promontory overlooking the Bosporus, was an ideal site. It was relatively close to both the Danube and Euphrates borders. There were excellent road communications both to east and west (though those in the west were vulnerable to disruption by invasion). In the Golden Horn it had a superb harbour.
The city had always controlled access to and from the Bosporus and so could be supplied by sea.
The Tetrarchic capitals with their palaces and adjoining hippodromes provided one model for the city, but a mass of statuary was looted from the Greek world (as it had been for Rome by earlier conquerors) and Constantine’s creation of a second senate and the provision of a free grain supply for its inhabitants (much of which came from Egypt) also suggested that this was more than just a subsidiary capital. As in Rome, there were seven ‘hills’, stretching back westwards from the core of the city, and’ like Rome, Constantinople was given fourteen administrative districts. The city’s hippodrome was directly modelled on the Circus Maximus in Rome and it was in its imperial box that Constantine, weighted with precious stones, displayed himself at the city’s inauguration in 330. Yet, in recognition of Aeneas and the founding of Rome, the city also echoed back to nearby Troy—its most prestigious (now vanished) baths, the Baths of Zeuxippos, were decorated with scenes from the Trojan legends. Yet one can hardly avoid the impression that the self-glorification of Constantine ranked high among the motives for the city’s foundation—a great statue of the emperor, with the rays of the sun emanating from his head, stood on a column in his Forum. Constantine spent much of his time in his new capital until his death in 337.
Interestingly Constantine gave low priority to the building of churches in Constantinople and it is possible that one motive for building the city was to retain its founder’s independence from the ancient Christian bishoprics. The only church completed by Constantine’s death, that of the Holy Apostles, was his own mausoleum where he had himself buried as no less than ‘the thirteenth apostle’. This somewhat provocative nomination provides further evidence of an emperor determined to maintain his own interpretation of his favoured religion. Even late in life Constantine kept his links with paganism. Coins issued on his death show him being welcomed into heaven with the same imagery as his pagan predecessors while the first ‘Christian’ churches in the city were dedicated to ‘Wisdom’ (the great Santa Sophia, still surviving today in its sixth-century form) and ‘Peace’ (Eirene), terminology acceptable to both Christians and pagans. The emergence of Constantinople as a predominantly Christian capital, a ‘Second Jerusalem’ according to some texts, only took place in the fifth century.