In one year, Constantine took the whole west and then Licinius took all of the east. Lactantius was the first to describe the decisive battles.
Constantine approached a Rome possessed by his rival and in the night God intervened …
Constantine was directed in a dream to cause the heavenly sign to be delineated on the shields of his soldiers, and so to proceed to battle. He did as he had been commanded, and he marked on their shields the letter X, with a perpendicular line drawn through it and turned round thus at the top, being the cipher of CHRIST. Having this sign, his troops stood to arms.
For his rival, it was
the anniversary of his reign. And God delivered:
The hand of the Lord prevailed, and the forces of Maxentius were routed.
Licinius’ army faced his rival’s and in the night God intervened …
And on the following night an angel of the Lord seemed to stand before Licinius while he was asleep, admonishing him to arise immediately, and with his whole army to put up a prayer to the Supreme God, and assuring him that by so doing he should obtain victory. Licinius fancied that, hearing this, he arose, and that his monitor, who was nigh him, directed how be should pray, and in what words. Awaking from sleep, he sent for one of his secretaries, and dictated …
Many copies were made of these words, and distributed amongst the principal commanders, who were to teach them to the soldiers under their charge. At this all men took fresh courage, in the confidence that victory bad been announced to them from heaven.
For his rival, this was
the anniversary of his reign. And God delivered …
Then were the troops of Daia slaughtered … The Supreme God did so place their necks under the sword of their foes, that they seemed to have entered the field, not as combatants, but as men devoted to death.
A visit in the night, an anniversary, victory thanks to God. With time, Constantine’s victory grew in statue and added marvels to become one of the strongest parts of his legend, while Licinius’ was forgotten along with the man himself.
Lactantius goes on to say that after his victory, Licinius reached the eastern capital, Nicomedia, and there he
returned thanks to God by issuing an edict …
When we, Constantine and Licinius, emperors, had an interview at Milan, and conferred together with respect to the good and security of the commonweal, it seemed to us that, amongst those things that are profitable to mankind in general, the reverence paid to the Divinity merited our first and chief attention, and that it was proper that the Christians and all others should have liberty to follow that mode of religion which to each of them appeared best.
Here’s the so-called Edict of Milan, which granted religious freedom to all and which later writers credited to Constantine alone.