Ammianus Marcellinus Res Gestae val1.6

[30] In commemoration of his splendid victory Constantine called Byzantium Constantinople after his own name; and as if it were his native city, he adorned it with great magnificence and wished to make it equal to Rome. Then he sought out new citizens for it from every quarter, ¹ and lavished such wealth on the city, that thereon he all but exhausted the imperial fortunes. There he also established a senate ² of the second rank, the members of which had the title of clari. ³

[31] Then he began war against the Goths, rendering aid also to the Sarmatians, who had appealed to him for help. ⁴ The result was that almost a hundred thousand of the Goths were destroyed by hunger and cold through Constantinus Caesar. ⁵ Then he also received hostages, among whom was Ariaricus, the king’s son.

[32] When peace with the Goths had thus been secured, Constantine turned against the Sarmatians, who were showing themselves to be of doubtful loyalty. But the slaves of the Sarmatians rebelled against all their masters ⁶ and drove them from the country. These Constantine willingly received, and distributed more than three hundred thousand people of different ages and both sexes through Thrace, Scythia, Macedonia, and Italy.

[33] Constantine was also the first Christian emperor, with the exception of Philippus ⁷ who seemed to me to have become a Christian merely in order that the one-thousandth year of Rome ⁸ might be dedicated to Christ rather than to pagan idols. ⁹ But from Constantine down to the present day all the emperors that have been chosen were Christians, with the exception of Julian, whose disastrous life forsook him in the midst of the impious plans which it was said that he was devising.

[34] Moreover, Constantine made the change ¹⁰ in a just and humane fashion; for he issued an edict that the temples should be closed without any shedding of pagan blood. Afterwards he destroyed the bravest and most populous of the Gothic tribes in the very heart of the barbarian territory; that is, in the lands of the Sarmatians.

[35] Constantine also put down a certain Calocaerus, ¹¹ who tried to achieve a revolution in Cyprus. He made Dalmatius, son of his brother of the same name, ¹² a Caesar; Dalmatius’ brother Hannibalianus he created King of Kings and ruler of the Pontic tribes, ¹³ after giving him his daughter Constantiana ¹⁴ in marriage. Then it was arranged that the younger Constantine should rule the Gallic provinces, Constantius Caesar the Orient, Constans Illyricum and Italy, while Dalmatius was to guard the Gothic coastline. ¹⁵ While Constantine was planning to make war on the Persians, he died in an imperial villa ¹⁶ in the suburbs of Constantinople, not far from Nicomedia, leaving the State in good order to his sons. He was buried in Constantinople, after a reign of thirty-one years. ¹⁷