In October of 312, a battle would take place that would not only make Constantine I the ruler of the entire Roman Empire but would change its course in history forever. The Battle of the Milvian Bridge took place between the Roman emperors Constantine I and Maxentius over who would become the ruler of the Roman Empire. It is better known, however, for being the catalyst for the conversion of the Romans to Christianity.
The Build-up to the Battle of Milvian Bridge
The path to war began following the abdication of emperor Diocletian in 305 AD. During this period, the Roman Empire was ruled under a ‘tetrarchy’. This system meant dividing the empire between two senior emperors known as ‘Augusti’ alongside their juniors and successors known as ‘Caesares’. At the time of Diocletian’s abdication, Constantine I was the son of Constantius I, the Caesar of the western Roman Empire. Maxentius was the son of Maximian, the Augustus of the western Roman Empire who retired alongside Diocletian.
When Diocletian and Maxentius abdicated, the struggle for power began. Constantius I was promoted to the role of Augustus of the western Roman Empire and Galerius was promoted to the role of Augustus of the eastern Roman Empire. When Constantius I died on 25 July 306, his troops in York proclaimed his son Constantine I as emperor. Eastern Roman Emperor Galerius recognized him as only Caesar of the western Roman Empire , not Augustus.
Statue of Constantine I, near York Minster, York, England. (Son of Groucho / CC BY 2.0 )
Unfortunately for Constantine, shortly after this his brother-in-law Maxentius had waged war against Galerius and seized Rome and Italy.
Maxentius felt he had been overlooked for the role of Caesar. His father had already overlooked him for the role following his abdication and he was not prepared to lose it again now that an opportunity had presented itself. He won the support of the Roman Senate and the Praetorian Guards (the personal bodyguards of the Roman Emperor) who declared him emperor. Galerius declared Maxentius a usurper and attempted to regain control but failed. By now, Constantine and Maxentius were headed for a collision course.
Despite the hostility between the two, it wouldn’t be until 312 that they would engage in open conflict. Constantine marched on Italy and swiftly had two major victories at Turin and Milan before successfully besieging Maxentius’ forces at Verona. He now had control over the three major cities in northern Italy. He began his march on Rome. Maxentius intended to wait it out behind the walls of Rome, cutting off all bridges into the city, but civil unrest grew quickly with people fearing Constantine’s fast-approaching army.
The modern day Milvian Bridge, Rome, from the south. (Tyler Bell / CC BY 2.0 )
Constantine’s Conversion to Christianity
It is at this stage that Constantine is said to have encountered a vision of some kind. Two different accounts report that on October 27, on the eve of the battle, Constantine had an omen or vision from the Christian God. The first account comes from a 4th century Christian writer called Lactantius. According to him, Constantine had a dream in which he was instructed to use the sign of the cross to defend himself from his enemies. The next morning he instructed his soldiers to paint Chi-Rho on their shields. These were the first two letters in a sacred monogram that means ‘Christ’ in Greek.
The second account comes from another 4th century Christian writer by the name of Eusebius of Caesarea. Eusebius actually gives two accounts of the battle that differ from each other. The first account comes from the ‘Historia ecclesiastica’ and does not mention any divine dream but does maintain that Constantine’s army was protected by God during the battle. In his later work, the ‘Vita Constantini’, he writes that Constantine and his army saw a vision of a cross hovering above the sun. This cross was inscribed with the words En toútōi níka meaning ‘In this, conquer’. That night, Constantine had a divine dream similar to the one described by Lactantius. The next morning, he converted to Christianity and ordered his troops to carry a labarum. This was a military flag that displayed the same Chi-Ro monogram that Lactantius described in his account.
Statue at York Minster bearing the line ‘By this sign Conquer’. (Smabs Sputzer / CC BY 2.0 )
The Battle of the Milvian Bridge took place on October 28th 312. It was an overwhelming success for Constantine I who annihilated Maxentius’ forces. Many of Maxentius’ troops, as well as Maxentius himself, died trying to flee across a temporary pontoon bridge they had constructed in preparation for battle. Having been broken by Constantine, they turned to flee across the bridge and overloaded it, causing it to collapse. The men fell into the river and drowned.
Detail of Constantine I on the Battle of Milvian Bridge fresco, the Vatican. ( CC BY-SA 2.0 )
Having won the battle, Constantine rode into Rome and was welcomed with open arms. He was given a military triumph. This was a ritual procession through the city of Rome celebrating the success of a victorious general. Usually, this triumph ended at the Capitoline temple where the general would offer a sacrifice to Jupiter. Constantine, however, refused to make a sacrifice at what was the most important pagan temple in Rome.
The Battle of the Milvian Bridge has been associated with the ascension of Constantine I as emperor of Rome as well as the triumph of Christianity over Roman paganism. Constantine would go on to reunite the Roman Empire under one ruler in 323 AD by defeating Licinius, the Eastern Roman Emperor.
Christianity was Constantine’s legacy to Europe and Byzantine civilisation . He is responsible for many major developments that were important to Christianity in Europe. In 313 AD he and Licinius jointly legalized Christianity with the Edict of Milan . He convened and presided over the Council of Nicaea in 325 which was the first effort to attain consensus in the Church and achieved the first uniform Christian doctrine, the Nicene Creed. He also funded the construction of many basilicas throughout Europe and in Jerusalem, including St. Peters Basilica in Rome. Few Roman Emperors can claim to have had such a lasting legacy that still impacts us today.
Top image: Fresco from the Vatican depicting the Battle of the Milvian Bridge that took place on October 28, 312 between the Roman emperors Constantine I and Maxentius. Source: CC BY-SA 2.0
By Mark Brophy