From: https://www.biographyonline.net/military/constantine.html
Constantine was a great military commander winning major victories over the Franks and Alamanni in 306-08, and later against the Visigoths in 332 and the Sarmatians in 334.
On 28 October 312, the forces of Maxentius met Constantine’s forces on the river Tiber. Constantine’s army was outnumbered 2:1. But, legends state that in the night he had a significant dream, where he had a vision of Jesus and was told to use the Christian cross. Constantine made his soldiers go into battle with the Christian cross and he made a promise that if successful in battle, he would adopt Christianity.
Eusebius, a Christian friend of Constantine describes this moment
“he saw with his own eyes in the heavens a trophy of the cross arising from the light of the sun, carrying the message, In Hoc Signo Vinces or “with this sign, you will conquer”
In the battle the following morning, Constantine was decisively victorious, and he was able to enter Rome on the next day. On entering Rome, Constantine embarked on a lengthy propaganda campaign to legitimise his rule and portray himself as a liberator over the tyrant Maxentius.
Constantine was able to consolidate his role, proving his military superiority over his rivals. In 313, he signed with Licinius the edict of Milan. This legalised Christianity and allowed freedom of worship. This edict was often ignored, but it was still an important moment with the principle of tolerating Christianity accepted within the Roman empire.
