How important was the Battle of the Milvian Bridge?

The Battle of the Milvian Bridge holds a significant place in history because of its influence on both the political landscape of the Roman Empire and the expansion of Christianity.

In the article below, WHE presents a brief overview of this important battle.

Multiple Roman Emperors – the Tetrarchy

The Roman Empire in the early 4th century AD was a vast, vast territory, and its administration was split among multiple emperors under a system called the Tetrarchy.

Emperor Diocletian

During Diocletian’s leadership, the empire regained stability, concluding the Crisis of the Third Century. In 286, he designated Maximian, a fellow officer, as the co-emperor or Augustus. While Diocletian governed the Eastern Empire, Maximian presided over the Western Empire.

This system, initiated by Emperor Diocletian (reign: 284 – 305), was intended to prevent civil wars and ensure smooth transitions of power, but it often led to rivalries and conflicts. Those conflicts reached serious proportions after Diocletian stepped down from power in 305.

After 299, under the Tetrarchy system, the map displays the dioceses and the designated zones of influence for each of the four tetrarchs, following the province exchange between Diocletian and Galerius. Image: Map of the Tetrarchy, which means the “Rule of Four”

Constantine (also known as Constantine the Great), realizing the complexity of the situation with multiple claimants in the east and knowing the challenges of fighting on multiple fronts, decided on a strategic wait-and-watch approach. Instead of hastily marching against them, he allowed the eastern claimants to confront each other, resulting in a weakened victor or the elimination of contenders.


By 312 AD, two contenders emerged for control of the Western Roman Empire: Constantine and Maxentius. The latter had been ruling Rome and parts of Italy, while Constantine controlled Gaul and Britain.

READ MORE: Roman Emperors Who Changed the Course of History

Prelude to the Battle

In 312 AD, Constantine decided to march on Rome to unseat his rival Maxentius. As he approached with an army that included Gallic and British forces, he is said to have had a vision in which he saw a Christian symbol (usually considered to be the Chi-Rho, ☧) and the words “In this sign, conquer.” Interpreting this as divine support, he had his soldiers mark their shields with the symbol.

Battle of Milvian Bridge in 312 AD

By 312 AD, Maxentius had emerged as the predominant force after successfully dealing with the eastern threats. Given the tensions and the territorial ambitions of both Constantine and Maxentius, it was clear that a direct conflict between these two powerful figures was on the horizon. Image (L-R): Busts of Roman Emperors Constantine the Great (reign: 306  -337) and Maxentius (reign: 306 – 312)

Events of the Battle

The battle took place on October 28, 312 AD. Maxentius decided to make his stand at the Milvian Bridge, which crossed the Tiber River on the northern outskirts of Rome. He believed the bridge would bottleneck Constantine’s forces, giving him an advantage.

Battle of Milvian Bridge in 312 AD

The Battle of the Milvian Bridge (1520–24) by Italian painter and architect Giulio Romano

Contrary to Maxentius’s expectations, the battle didn’t go in his favor. Constantine’s forces launched a ferocious attack, and during the chaos, the bridge either collapsed or became too overcrowded. Maxentius was among those who drowned in the Tiber.

A day after his famed victory, Constantine marched unimpeded into Rome.

Did you know…?

  • Maxentius also reportedly received a prophecy that on October 28, the enemy of Rome would perish, leading him to believe that he would win the battle on that day.
  • On his way to Milvian Bridge, Constantine and his generals secured victory over Maxentius at a number of places, including Verona and Turin.

What happened after the battle?

Constantine’s victory at the Milvian Bridge made him the undisputed ruler of the Western Roman Empire. Within a short period, he would also secure the East, becoming the sole emperor of a reunified Roman Empire.

The battle had profound religious implications. Constantine attributed his victory to the Christian god. In 313 AD, he and his co-emperor in the East, Licinius, issued the Edict of Milan, which proclaimed religious tolerance throughout the empire and effectively legalized Christianity. This edict marked the beginning of the end for centuries of state-sanctioned persecution against Christians.

Constantine himself eventually converted to Christianity and became one of its most influential proponents, laying the foundation for it to become the dominant religion in the Roman Empire and subsequently in Europe.

A contemporary image of the battle from the Arch of Constantine, Rome. It shows Constantine’s cavalry driving Maxentius’ troops into the waters of the Tiber.


The Battle of the Milvian Bridge is not just a military event; it’s a nexus point where politics, personal ambition, and religious evolution met and changed the trajectory of Western civilization.

Questions & Answers

Constantine and Maxentius: Two of the primary contenders for control of Western Roman Empire in the early part of the 4th century AD. Image: Battle at the Milvian Bridge, Audran after Le Brun

The Battle of the Milvian Bridge, while primarily a political and military conflict, also played a pivotal role in the history of Christianity, marking the beginning of its transformation from a persecuted sect to the state religion of the Roman Empire.

Here are some of the frequently asked questions about the battle:

When did the battle take place?

The battle took place on October 28, 312 AD.

What was the size of their forces?

According to historians of the era, Constantine marched about 41,000 to face off against Maxentius. His opponent had in the region of 45,000 forces.

Where is Milvian Bridge?

The Milvian Bridge spans the Tiber River in Rome, Italy. The bridge is known in Italian as Ponte Milvio or Ponte Molle. In Latin, it is called Pons Milvius or Pons Mulvius.

The Milvian (or Mulvian) Bridge is over the Tiber in northern Rome, Italy.

Main cause of the battle?

The battle was a result of the tetrarchy system established by Emperor Diocletian. This system intended to provide an orderly imperial succession, but it led to power struggles. By 312 AD, the Roman Empire was divided among multiple rulers, leading to civil wars.

Battle of Milvian Bridge in 312 AD

What did Constantine do after having the vision?

As Constantine was marching to confront Maxentius, he reportedly had a vision in which he saw a Christian symbol (often described as the Chi-Rho) accompanied by the words “In this sign, conquer.” Taking this as a divine sign, Constantine had his soldiers paint the symbol on their shields.

Missorium depicting Constantine’s son Constantius II, accompanied by a guardsman with the Chi Rho monogram depicted on his shield.

What was the importance of the Battle of Milvian Bridge?

With his victory over rival emperor Maxentius, Constantine the Great became the sole ruler of the Western Roman Empire.

Constantine then went ahead to attribute the victory to the Christian god. This particular event is generally viewed by historians as a turning point in the Christianization of the Roman Empire.

The above explains why in 313 AD, Constantine and his eastern co-emperor Licinius issued the Edict of Milan, which granted religious tolerance to Christians and allowed them to practice their faith openly without fear of persecution.

After his famed victory at Milvian Bridge, Constantine the Great converted to Christianity; by so doing, he became the first Roman emperor to do so. The emperor spent his later years being one of Christianity’s most significant patrons. Image: Modern bronze statue of Constantine I in York, England

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