Maxentius, who was Maximian's son and Constantine's brother-in-law, declared himself emperor at Rome in 306 and "Augustus" in 307. He took control over most of Italy and also Sicily, Corsica, Sardinia, and North Africa.
More civil wars broke out, with Galerius, Maxentius, Maximian and Constantine taking turns in attempting to become sole emperor. Finally, Constantine crossed the Alps Mountains in 312 with a small army and defeated Maxentius and his forces at Turin and Verona in northern Italy. He continued on and fought Maxentius for control of the empire.
Constantine and his troops camped near the Milvian Bridge, which is over the Tiber River. On the night before the battle at this bridge, Constantine claimed that he saw a sign from heaven, an image of a cross of lights. On this cross was the phrase in hoc signo vinces, which means "you will conquer by this sign." He said that Christ appeared to him later that night in his sleep and commanded him to make a likeness of that sign and to use it as a sign against his enemies.
This was something completely new to Constantine. Throughout his early life, Constantine believed in the Roman sun god Sol. Sol supposedly was the principal being behind the universe. Constantine knew about the Christians, who believed in Jesus Christ, the one God. He also knew that Diocletian had persecuted the Christians for their beliefs.
Constantine's beliefs began to change on the night before the Battle at Milvian Bridge. He ordered his troops to fight under the sign of the cross. Another version of this story says that Constantine ordered the first two Greek letters in the name Christ (P and X, Chi and Rho) to be drawn on all of his soldiers' shields. It is said that with these marks Constantine was able to defeat Maxentius at the Milvian Bridge on the Tiber River. This victory added Italy and North Africa to his empire. After winning the battle, Constantine believed that the Christians' god helped him with his victory. He showed his respect for this religion by giving its members the freedom to practice it.
Constantine won the battle and control of the western half of the Roman Empire. He shared power with Licinius, who controlled the eastern provinces. They met in the city of Milan and agreed to give the right of free worship to all religious groups. Constantine recognized the Christians as a legal body that should have the right to hold property. He returned property that had been seized from them under earlier emperors. This was a very important result of the meeting and is known as the Edict of Milan. Constantine was so grateful for his victory over Maxentius that he insisted on permitting the Christians and people who followed other religions to exist freely. He persuaded Licinius to do the same. Even though the Christians were not many, they were growing in number. With Constantine's support of this new religion, very many Romans converted during his reign.
Constantine did not become a Christian at this point. He remained half-pagan for a time even though he adopted the cross as his symbol. The non-Christians still continued to honor Constantine and built the Arch of Constantine in the year 315 to pay homage to his victory over Maxentius (as shown below).
