The Battle of the Milvian Bridge took place between the Roman Emperors Constantine I and Maxentius on 28 October 312. It was named after the Milvian Bridge, a major route over the Tiber. Constantine won the battle and began the march that led him to end the Tetrarchy and become the sole ruler of the Roman Empire. Maxentius drowned in the Tiber during the battle. His body was later recovered from the river and beheaded; his head lingered in the streets of Rome the day after the battle, and was then displayed in Africa.
According to chroniclers such as Eusebius of Caesarea and Lactantius, the battle marked the beginning of Constantine”s conversion to Christianity. Eusebius Caesarea recounts that Constantine and his soldiers had a vision sent by the Christian God. This was interpreted as a promise of victory, as long as the sign XP, the first two letters of Christ”s name, was painted on the soldiers” shields. The Arch of Constantine erected to celebrate the victory certainly attributes Constantine”s success to divine intervention. However, the monument does not display overtly Christian symbolism.
The underlying causes of the battle were the rivalries inherent in Diocletian”s Tetrarchy. After Diocletian abdicated on May 1, 305, his successors began fighting for control of the Roman Empire almost immediately. Although Constantine was the son of the Emperor in the West, Constantius I, the institution of the Tetrarchy did not necessarily provide for hereditary succession. When Constantine I died on 25 July 306, his father”s troops proclaimed Constantine as Augustus at Eboracum (York). But in Rome, the eunuch (successor) was Maxentius, the son of the former Emperor in the West (when Constantine I was Caesar), Maximian, who took the title of Emperor on 28 October 306. Constantine I”s claim was recognized by Galerius, Emperor in the East, while Maxentius was treated as a usurper. Galerius, however, had recognized Constantine as holding only the lesser imperial rank of Caesar. Galerius ordered Caesar II. Severus to subdue Maxentius in early 307. Once Severus arrived in Italy, however, his army defected to Maxentius. Severus was arrested, imprisoned and executed. Galerius himself marched on Rome in the autumn, but failed to take the city. Constantine avoided conflict with both Maxentius and the Emperor and Caesar in the East for most of this period.
By 312, however, Constantine and Maxentius were engaged in open hostility towards each other, although they were brothers-in-law through Constantine”s marriage to Fausta, Maxentius” sister: in the spring of 312 Constantine gathered an army of 40,000 soldiers and decided to expel Maxentius himself. He easily conquered northern Italy, winning two major battles: the first near Turin, the second at Verona, where the Prefect of Praetorium, Ruricius Pompeianus, Maxentius” senior general, was killed.
It is commonly understood that on the night of October 27, with the armies preparing for battle, Constantine had a vision that led him to fight under the protection of the Christian God. Some details of this vision, however, differ among the sources that report it.
Lactantius reports that on the night before the battle, Constantine was instructed in a dream to “draw the heavenly emblem on the shields of his soldiers” (On the Deaths of the Persecutors 44.5). He followed the instructions of his dream and engraved the shields with an emblem “declaring Christ”. Lactantius describes this emblem as a “cross-mark,” a cross with its upper end rounded in a manner resembling a P. There is no certain evidence that Constantine ever used this mark, unlike the more familiar HP emblem described by Eusebius.
From Eusebius two testimonies about the battle survive. The first, shorter one, in the Ecclesiastical History, promotes the belief that the Christian God helped Constantine, but does not mention a vision. In the later Life of Constantine, Eusebius gives a detailed account of a vision and emphasizes that he had heard the story from the Emperor himself. According to this version, Constantine I was marching with his army (Eusebius does not specify the actual location of the event, but clearly not at the camp in Rome) when he looked towards the sun and saw above it a cross of light and with it the Greek words “En Tuto Nika”, usually translated into Latin as in hoc signo vinces. The literal meaning of the phrase in Greek is “with this (sign), conquer” while in Latin it is “with this sign, you will conquer”. A more accurate translation would be “through this sign you will conquer”. At first he was unsure of the meaning of the apparition, but the next night he had a dream in which Jesus explained that he was to use the sign against his enemies. Eusebius then goes on to describe the labarum, the military insignia used by Constantine in his later wars against Licinius, showing the symbol XP.
The accounts of the two contemporary writers, though not entirely consistent, have merged into one popular understanding, that Constantine saw the XP emblem the night before the battle. Both authors agree that the sign was not widely understood to denote Christ (although among Christians, it was already used in catacombs along with other special symbols to mark and decorate Christian tombs). Its first imperial appearance is on a silver coin of Constantine c. 317, proving that Constantine I used the emblem at that time, though not very conspicuously. He made more extensive use of the KP and laver later, during the conflict with Licinius.
Some have viewed the vision as a solar phenomenon (e.g., the solar halo called a parhelion), which may have preceded Christian beliefs, later expressed by Constantine I. Coins of Constantine I depicting him as the consort of a solar deity were minted until 313, the year following the battle. The solar deity Sol Invictus is often depicted with an alto (nimbus, halo). Various emperors depicted the Sun Invictus on their official coins, with a wide range of inscriptions. Some incorporated the adjective invictus, as in the inscription SOLI INVICTO COMITI, which refers to the Emperor as a companion (follower) of the Unconquered Sun, an inscription used with particular frequency by Constantine. Constantine”s official coinage continued to bear images of the Sun until 325
Constantine arrived in Rome at the end of October 312, approaching along the Via Flaminia. He camped at Malborghetto near the Prima Porta, where the remains of a monument to Constantine, the Arch of Malborghetto, still survive in commemoration of the event there.
It was expected that Maxentius would remain in Rome and withstand a siege. He had successfully employed this strategy twice before, during the invasions of Severus and Galerius. Indeed, Maxentius had organized the storage of large quantities of food in the city in preparation for such a development. Surprisingly, he decided otherwise, choosing to meet Constantine in open battle. Ancient sources commenting on these events attribute this decision either to divine intervention (e.g. Lactantius, Eusebius) or superstition (e.g. Zosimus). They also note that the day of the battle was the same as the day of his ascension (28 October), which was generally considered a good omen. Furthermore, Maxentius is reported to have consulted the prophetic Sibylline Books, which stated that “on October 28 an enemy of the Romans would be lost”. Maxentius interpreted this prophecy as favourable to himself. Lactantius also reports that the people supported Constantine with cheers during the horse races.
Maxentius chose to stand in front of the Milvio Bridge, a stone bridge on Flaminia Street over the Tiber River in Rome (the bridge stands today on the same site, somewhat restored, and is called in Italian Ponte Milvio or sometimes Ponte Molle, “soft bridge”). Its preservation was vital if Maxentius was to keep his rival out of Rome, as the Senate would surely favour whoever held the city. As Maxentius had probably partially destroyed the bridge during his preparations for a siege, he constructed a wooden or floating bridge for his army to cross the river. Sources vary as to the nature of the bridge, which was central to the events of the battle. Zosimus vaguely states that it was constructed in two sections, connected by iron ties, while others describe it as a floating bridge. The sources are also unclear whether the bridge was deliberately constructed to collapse as a trap for Constantine”s forces or not.
The next day the two armies clashed and Constantine won a decisive victory. Maxentius” deployment may have been incorrect, as his troops seem to have been deployed with the Tiber River very close to their rear, giving them little room to regroup in case their formations were forced to retreat. Already known as a skilful general, Constantine first attacked Maxentius” cavalry with his cavalry and broke through it. Constantine”s infantry then advanced. Most of Maxentius” troops fought well, but began to push back towards Tiberius. Maxentius then decided to order a retreat, intending to make another stop at Rome itself. However, there was only one route of escape, that by way of the bridge. Constantine”s men inflicted heavy losses on the retreating army. Finally the temporary bridge (which had been erected next to the Milvian Bridge), over which many of Maxentius” troops were escaping, collapsed and those who had been blocked on the north bank of the Tiber were either captured or killed. The Praetorian Guard of Maxentius, which had originally proclaimed him emperor, seems to have made a stubborn resistance on the north bank of the river; “as an expression of their apology, they covered with their bodies the place they had chosen for battle.”
Maxentius was among the dead: he drowned in the river while trying to swim across it in an attempt to escape or, alternatively, it is described that his horse threw him into the river. Lactantius describes the end of Maxentius in the following way: “The bridge at his back collapsed. Seeing this, the battle became hotter. The hand of the Lord prevailed and Maxentius” forces were overwhelmed. He fled towards the broken bridge, but the crowd that pressed on him led him on foot to Tiberius”
Constantine entered Rome on 29 October. He organised a magnificent arrival ceremony in the city (adventus) and was met with popular jubilation. Maxentius” body was recovered by Tiberius and beheaded. His head was passed through the streets for all to see. After the ceremonies, Maxentius” head was sent to Carthage as proof of his fall, so Africa offered no further resistance. This battle gave Constantine undisputed control of the western half of the Roman Empire. Descriptions of Constantine”s entry into Rome fail to mention that he ended his procession at the Temple of the Capitoline Zeus, where sacrifices were usually offered. Although often used to show Constantine”s Christian sensibilities, this omission cannot be taken as evidence that Constantine was a Christian at this point. He chose to honour the Senatorial Curia with a visit, where he promised to restore its old privileges and give it a secure part in his reformed government; there would be no revenge against the supporters of Maxentius. Maxentius was condemned to damnatio memoriae, all his legislation was annulled, and Constantine usurped all Maxentius”s important building works in Rome, such as the Temple of Romulus and the Basilica of Maxentius. Maxentius” strongest supporters in the army were neutralized when the Praetorian Guard and the Personal Equites Singulares were disbanded. Constantine is believed to have replaced these imperial garrisons with a series of cavalry units called the Palatine Schools (Scholae Palatinae).
Paul K. Davis writes that “Constantine”s victory gave him total control of the Western Roman Empire, paving the way for Christianity to become the dominant religion for the Roman Empire and eventually for Europe.” The following year, 313, Constantine and Licinius issued the Edict of Mediolan, which made Christianity officially recognized and thus tolerated as a religion in the Roman Empire.
The most important ancient sources on the battle are Lactantius, De mortibus persecutorum 44; Eusebius of Caesarea, Ecclesiastical History ix, 9 and Life of Constantine i, 28-31 (and the Panegyrici Latini of 313 (anonymous) and 321 (by Nazarius).