Roman Empire: Battle of the Milvian Bridge

The Battle of Milvian Bridge was part of the Wars of Constantine.

Constantine defeated Maxentius on October 28, 312.

Constantine

• Emperor Constantine I
• approximately 100,000 men

Maxentius

• Emperor Maxentius
• approximately 75,000-120,000 men

In the power struggle that began following the collapse of the Tetrarchy around 309, Constantine consolidated his position in Britain, Gaul, the Germanic provinces, and Spain. Believing himself to be the rightful emperor of the Western Roman Empire, he assembled his army and prepared for an invasion of Italy in 312. To the south, Maxentius, who occupied Rome, sought to advance his own claim to the title. To support his efforts, he was able to draw upon the resources of Italy, Corsica, Sardinia, Sicily, and the African provinces.

Advancing south, Constantine conquered northern Italy after crushing Maxentian armies at Turin and Verona. Showing compassion to the citizens of the region, they soon began to support his cause and his army swelled to near 100,000 (90,000+ infantry, 8,000 cavalry). As he neared Rome, it was expected that Maxentius would stay within the city walls and force him to lay siege. This strategy had worked in the past for Maxentius when he faced invasion from the forces of Severus (307) and Galerius (308). In fact, siege preparations had already been made, with large amounts of food already brought into the city.

Instead, Maxentius opted to give battle and advanced his army to the Tiber River near the Milvian Bridge outside of Rome. This decision is largely believed to have been based on favorable omens and the fact that the battle would occur on the anniversary of his ascension to the throne. On October 27, the night before the battle, Constantine claimed to have had a vision which instructed him fight under the protection of the Christian God. In this vision a cross appeared in the sky and he heard in Latin, "in this sign, you will conquer."

The author Lactantius states that following the vision's instructions, Constantine ordered his men to paint the Christians' symbol (either a Latin cross or the Labarum) upon their shields. Advancing over the Milvian Bridge, Maxentius ordered it destroyed so that it could not be used by the enemy. He then ordered a pontoon bridge constructed for his own army's use. On October 28, Constantine's forces arrived on the battlefield. Attacking, his troops slowly pushed back Maxentius' men until their backs were at the river.

Seeing that the day was lost, Maxentius decided to retreat and renew the battle closer to Rome. As his army withdrew, it clogged the pontoon bridge, its only avenue of retreat, ultimately causing it to collapse. Those trapped on the north bank were either captured or slaughtered by Constantine's men. With Maxentius' army split and decimated, the battle came to a close. Maxentius' body was found in the river, where he had drowned in an attempt to swim across.

While casualties for the Battle of the Milvian Bridge are not known, it is believed that Maxentius' army suffered badly. With his rival dead, Constantine was free to consolidate his hold over the Western Roman Empire. He expanded his reign to include the entire Roman Empire after defeating Licinius during the civil war of 324. Constantine's vision prior to the battle is believed to have inspired his ultimate conversion to Christianity.

Selected Sources

• Constantine the Great
• Lactantius' Account of the Battle
• Eusebius' Life of Constantine