October 28, 312 A.D. Constantine defeated Maxentius in the Battle of Milvan Bridge. It was a battle that changed history. It was the first of Constantine's major victories in his consolidation of the Roman Empire, and it marked day when Christianity went from being persecuted to being on a trajectory to dominate Europe.
Christianity had been under periodic persecution by the Roman Empire ever since Nero used Christians as scapegoats for the fire that consumed Rome in 64 A.D. As late as 303 A.D., the most bloody of the persecutions came at the direction of the Roman Emperor Diocletian. Constanine himself was not born a Christian. He would grow into Christianity over his lifetime, with perhaps the most notable event in his conversion being the events that took place just prior to the Battle of Milvan Bridge.
Constantine was born in 272 A.D., the son of a Roman sub-Emperor who held control over a portion of Rome's divided empire. By 312 A.D., Constantine had taken over his father's command and was drawn into a war for control of the empire. The night of October 27, 312, found Constantine north of the Milvan Bridge on the Tiber River, his army of 100,000 men preparing to attack an army twice its size led by Maxentius.
According to legend, on the march to the Tiber, Constantine had a vision of a cross arising out of the sun, marked with the phrase In Hoc Signo Vinces - under this sign, you will conquer. In camp on the night of the 27th, Constantine claims to have a dream of Christ, who explained to him the meaning of the sign and that, if he would but adopt the sign for his army, they would conquer. When battle was joined on the 28th, Constantine's forces marched under the cross - and Constantine won a decisive victory.
Maxentius chose to make his stand in front of the Milvian Bridge, a stone bridge that carries the Via Flaminia road across the Tiber River into Rome (the bridge stands today at the same site, somewhat remodelled, named in Italian Ponte Milvio . . .). Holding it was crucial if Maxentius was to keep his rival out of Rome, where the Senate would surely favour whoever held the city. As Maxentius had probably partially destroyed the bridge during his preparations for a siege, he had a wooden or pontoon bridge constructed to get his army across the river. . . .
The next day, the two armies clashed, and Constantine won a decisive victory. The dispositions of Maxentius may have been faulty as his troops seem to have been arrayed with the River Tiber too close to their rear, giving them little space to allow re-grouping in the event of their formations being forced to give ground.
Already known as a skillful general, Constantine first launched his cavalry at the cavalry of Maxentius and broke them. Constantine's infantry then advanced, most of Maxentius's troops fought well but they began to be pushed back toward the Tiber; Maxentius decided to retreat and make another stand at Rome itself; but there was only one escape route, via the bridge. Constantine's men inflicted heavy losses on the retreating army. Finally, the temporary bridge set up alongside the Milvian Bridge, over which many of the troops were escaping, collapsed, and those men stranded on the north bank of the Tiber were either taken prisoner or killed. Maxentius' Praetorian Guard seem to have made a stubborn stand on the northern bank of the river. Maxentius was among the dead, . . .
The Battle of Milvan bridge set the stage for triumph of Constantine and, with him, the triumph of Christianity in the Western World. In 313 A.D., Constantine promulgated the Edict of Milan, ending all religious persecution in the Roman Empire and restoring to Christians their titles and property. Constantine became a dedicated patron of the Church. He "built basilicas, granted privileges to clergy (e.g. exemption from certain taxes), [and] promoted Christians to high office . . . His most famous building projects include the Church of the Holy Sepulchre, and Old Saint Peter's Basilica." Constantine also called the First Eccumenical Council of the Church, the Council of Nicaea, in an effort to standardize Christian teachings and ritual.