This Day in History: The Battle of the Milvian Bridge

The Arch of Constantine in Rome. Situated between the Palatine Hill and the Colosseum, the triumphal arch was dedicated in 315 to commemorate the Emperor's victory over Maxentius at the Battle of the Milivian Bridge
Photo by New York Scugnizzo

By Giovanni di Napoli

On October 28, 312 AD Emperor Constantine the Great defeated the usurper Maxentius at the Battle of the Milvian Bridge. The victory definitively ended the Roman Empire’s period of Tetrarchy (leadership of four people) established by Diocletion in 293 and set the stage for Constantine’s eventual ascension to sole rule of the empire.

According to tradition, after defeating Maxentius’ forces in northern Italy Constantine advanced south to the Tiber River outside of Rome. At the Milvian Bridge (Ponte Milvio) Constantine found his enemy mobilizing for battle instead of safely preparing for a siege behind Rome’s walls. Looking to the heavens, he invoked the help of Summus Deus, or the greatest god. 

That night, Constantine dreamt of the Chi and the Rho (XP), the first two letters of Christ’s name in Greek, and heard a voice proclaim “In Hoc Signo Vinces,” which means “By this sign you will conquer.”

At dawn, the Emperor had a vision of the Cross rising from the light of the sun and ordered his legion’s to paint the Chi and the Rho on their shields. The symbol and the Cross were also affixed to the Emperor’s golden standard (labarum).

Arrayed before the bridge the two armies clashed. After much valor, struggle and bloodshed, Constantine eventually won the day and routed his enemy. Attempting to flee the field of battle, Maxentius was thrown from his horse and drowned in the Tiber. The corpse was fished from the river and put on show to allay any doubts about Constantine's decisive victory.  

Entering Rome in triumph on October 29th, Constantine was acknowledged as the Western Emperor. He converted to Christianity and legalized the faith in 313, thus ending 300 years of Christian persecution by the Romans.

With Emperor Licinius’ victory over Emperor Maximinus II in the East (313) and Constantine’s subsequent victory over Licinius at the Battle of Chrysopolis on September 18, 324, he became the sole emperor of the Roman Empire.

Choosing the strategic city of Byzantium to be the Empire's new capital, on May 11, 330 he renamed it Constantinople after himself.