Milvian Bridge – Constantine’s Victory






27 October 312

Forces Engaged

Gallic: Approximately 50,000 men. Commander: Constantine.

Italian: Approximately 75,000 men. Commander: Maxentius.


Constantine’s victory gave him total control of the western Roman Empire, paving the way for Christianity as the dominant religion for the Roman Empire and ultimately for Europe.

Historical Setting

Rarely has the course of events followed such a convoluted path to a single decisive event as those that took the forces of the western Roman Empire to the battle at Milvian Bridge. In the 49 years between 235 and 284, Rome was ruled by no less than 26 emperors. Almost anyone with the support of a legion or two battled for, seized, and lost the position of supreme ruler of the Roman Empire. Finally, in 284, Diocletian seized and kept power. Although a soldier from Illyria (along the eastern Adriatic coast), Diocletian, once in power, spent most of his time trying to institute reforms that would stabilize the empire. This involved increased taxation, but the collection was done in a much more equitable fashion than in previous decades. The money was spent on increased bureaucracy and military to the point that some believed there to be more employees of the government than there were taxpayers.

While that did bring about a much more stable atmosphere, Diocletian’s most serious reform involved the system by which the empire was ruled. Realizing that no one man could possibly manage everything from Britain to Persia, Diocletian introduced a tetrarchy, rule by four men. Basing his capital in Nicomedia, at the western end of the Sea of Marmora, he appointed a co-emperor, Maximian, to rule from Italy. Both Diocletian and Maximian would hold the title of augustus. Each man appointed a subordinate, called a caesar, to assist them in ruling their respective halves of the empire. Diocletian named Galerius as caesar in the east, and Maximian named Constantius as caesar in the west. The caesar was to replace the augustus upon his death or retirement and then name a replacement caesar for himself. This was meant to ensure a regular succession, which had not existed for many decades.

When Diocletian decided to retire in 305, he convinced Maximian to do so as well. As planned, Constantius and Galerius rose to augustus, but then they named Flavius Severus as caesar in the west and Maximinus Daia in the east, respectively. Naming those two as caesars seemed a slap in the face to the two who thought that by birth they should have had the positions: Constantine, as son of Constantius, and Valerius Maxentius, as son of Maximian. That resentment came to a head when Constantius died in 306. His army, based in Britain and Gaul, named Constantine not just caesar but augustus, although Constantine declined the higher title. He was confirmed as caesar, but Severus, as acting caesar, became augustus in the west. Unfortunately, troops in Italy named Maximian’s son Maxentius as augustus, ignoring Severus who was next in line. That resulted in a civil war between 306 and 307 in which Severus was finally executed and Maxentius took the western augustus title, but ceded it to his father Maximian who came out of retirement to reoccupy the throne.

Rather than leave well enough alone, Galerius in the eastern empire refused to recognize either Constantine or Maximian as western augustus. Instead, Galerius named one of his generals, Licianus Licinius, as augustus to replace Severus, and he invaded Italy to enforce that appointment. During the invasion, Maxentius forced his father out of power and named himself western augustus. To make matters even more confusing, Galerius’s nephew Maximinus Daia sought and received the title of augustus as well. Thus, six men held the title originally intended for two, while the post of caesar remained vacant. Diocletian finally stepped in, calling a conference in 308 at Carnuntum (modern Hainburg, Austria). Each man except Maximian (retiring a second time) was allowed to retain the title of augustus and was given control over separate regions of the empire.

Diocletian’s mandate lasted but 2 years. Maximian, fleeing from his son to the court of Constantine in Gaul, tried to overthrow his host in 310. For his trouble, he was taken prisoner and allowed to kill himself. When Galerius died in 311, once again four men reigned, all as augustus and none as caesar: Constantine in Gaul, Maxentius in Italy, Licinius in the Balkans, and Maximinus Daia in the east. Had Constantine formally ceded the title of augustus and held that of caesar, Maxentius may never have felt the need to go to war against him. Maxentius, however, was a tyrannical ruler who spent lavishly on himself and his Praetorian Guard while abusing the common people; such men see conspiracies everywhere, and Maxentius suspected Constantine of plotting against him. Determined to rule the western half of the empire alone, in 311 Maxentius began preparations for an invasion of Gaul.

The Battle

Learning of Maxentius’s intentions, Constantine decided to strike first. He had some 100,000 troops under his command, but more than half had to be left to protect the German and British frontiers. In the early spring of 312, Constantine marched his army of 40,000 through the melting alpine snow into northern Italy. Maxentius sent troops northward under a variety of generals, whom Constantine proceeded to defeat at Susa, Turin, and Milan, each of his victories coming over superior numbers. Maxentius sent his best general last; Ruricius Pompeianus too was defeated at Brescia and Verona. As he fought his way south, Constantine maintained a fairly stable number in his army, picking up recruits from the countryside and his defeated enemies. As he approached Rome, his force numbered about 50,000 men. Maxentius, locked up in Rome, commanded about 75,000.

The events that occurred just outside Rome are the stuff of legend. Maxentius misread the omens he received. He was advised via the Sybilline books concerning the upcoming battle “that on that day the enemy of Rome should perish” (Dudley, The Romans, p. 270). Convinced that Constantine and not he himself was the enemy of Rome, Maxentius led his army out from behind the Roman Walls of Aurelian onto the plains near the village of Saxa Rubra, deploying them with the Tiber River at his back.

Constantine also received an omen. The day before the battle, it is said that he had a vision. This vision has been described in a variety of ways, depending on one’s source. Durant’s description, citing the contemporary source Eusebius, says that Constantine saw in the sky a flaming cross, upon which was written the Greek words en tutoi nika, “in this sign conquer.” The following morning, Constantine heard a voice instructing him to place upon his soldiers’ shields “the letter X with a line drawn through it and curled around the top—the symbol of Christ” (Durant, Caesar and Christ, p. 654). Most sources put the wording on the cross as Latin: in hoc signo vinces. Dudley (The Romans, p. 270) states that Constantine had a dream before the battle in which he was told to place the Greek letters chi and rho (the sign of Christ) on his army’s shields.

Constantine had in his army a number of Christians, as well as followers of the equally popular Mithra cult. The followers of Mithra used a cross of light as symbolic of the Unconquerable Sun, a sign of their god. Constantine had also long been a believer in the cult of Apollo, the sun god. At any rate, Constantine later told Eusebius that he vowed before the battle to convert to Christianity if he was victorious.

Details of the battle are sketchy. It seems that both sides placed infantry in the center and cavalry on the flanks. Constantine commanded one of the cavalry wings and led the charge. His Gallic cavalry was more mobile than the heavily armored Roman cavalry under Maxentius, but was heavier than the lightly armed North African cavalry auxiliaries. Thus, it was able to outfight both and crush Maxentius’s flanks. Among the infantry, this caused much panic, and only the Praetorian Guard stood their ground against the attacks of Constantine’s infantry. They were over-whelmed and died where they stood. The rout of the remainder of Maxentius’s force had but one escape route, that of the Milvian Bridge across the Tiber. It was so crowded and the troops so desperate that not even Maxentius could get onto it. He tried to swim across, but the weight of his armor dragged him to his death. His body was brought to the surface the next day.


Maxentius’s death meant that Constantine was the sole ruler of the western Roman Empire. Just before he launched his invasion, Constantine had concluded a truce with Licinius. The agreement included the promise of marriage to Constantine’s sister for Lucinius’s impassivity during the campaign. Licinius was as good as his word, and once the situation had settled down, he and Constantine met in Milan in February 313. There the two issued the Edict of Milan concerning religious tolerance. “I, Constantine Augustus, and I, Licinius Augustus, met under good auspices in Milan, we discussed everything bearing on public advantage and security. First, we considered regulations should be framed to secure respect for divinity on these lines: that the Christians and all other men should be allowed full freedom to subscribe to whatever form of worship they desire, so that whatever divinity may be on the heavenly throne may be well disposed and propitious to us, and to all placed under us” (Dudley, The Romans, p. 271). Constantine seemed to be hedging his bets here, but as time went by he became more solidly supportive of Christianity.

Constantine was soon back in the field, campaigning against hostile Germanic tribes, while Licinius fought and defeated Maximinus Daia. This defeat placed Licinius in control of the eastern Roman Empire. For the next 11 years, the two alternately supported and fought each other. When Constantine defeated Licinius at a battle in 314 and took from him control of almost everything in Europe, Licinius responded by persecuting Christians in the east. He maintained his pagan ways as Constantine became more Christian, until a final showdown between the two resulted in Licinius’s defeat in 323; he was executed the following year.

The city of Rome, which had become an increasingly less important city, lost its title as capital of the empire when Constantine established the city bearing his name, Constantinople. Over time, it became not only the political center of the empire but rivaled Rome for centuries as headquarters of the Christian faith. It was Constantine’s victory outside Rome in 312, however, that put the Christians in a position to be arguing over where the power in their church should rest. The ban on persecution issued in Milan gave the Christians the first breathing room in their history. By 325, they were virtually guaranteed preeminence, for in that year Constantine summoned the Council of Nicea. There leaders of the Christian church branded certain beliefs to be heresies; unfortunately for history, Constantine blamed the Jews for Christ’s death, setting in motion centuries of pogroms.

The depth of Constantine’s conversion has been debated since his own day. The primary source for his statements of faith come from the contemporary Christian historian Eusebius, who was more than a little biased. Certain later statements attributed to the emperor give conflicting views. Constantine rarely followed Christian rituals, and, even though he expressed some religious views at the Council of Nicea, he was more interested in maintaining order than leading the church. His mother was a strong convert and certainly had some influence on him, but, whether he was a Christian by conversion or for political ends, the Christian Church benefited. Other religions soon found themselves persecuted just as harshly by the Christians as the Christians themselves formerly had been. Whatever the merits and drawbacks of later interreligious strife, the fact that Christianity is the dominant faith in Europe today is directly traceable to Constantine.

His foundation of Constantinople set up the division of the Roman Empire into two formal halves. The Eastern Roman Empire grew in power and wealth, later being titled the Byzantine Empire. It stood until overthrown by the power of Islam in 1453. The Western Roman Empire sunk into mediocrity, with occasional glimpses of its former glory when a passing tribe exercised enough power to establish any stability there. Ultimately, Rome came to be a religious rather than a political capital, and its later power emanated from the papacy rather than from the emperor.


Dudley, Donald. The Romans. New York: Alfred A. Knopf, 1970; Durant, Will. Caesar and Christ. New York: Simon & Schuster, 1944; Eusebius. The History of the Church from Christ to Constantine. Translated by G. A. Williamson. New York: Dorset Press, 1984 [1965]; Gibbon, Edward. The Decline and Fall of the Roman Empire. Abridged by Frank Bourne. New York: Dell, 1963; Grant, Michael. Constantine: The Man and His Times. New York: Charles Scribner’s Sons, 1994. Barnes, Timothy D. Constantine and Eusebius. Cambridge: Harvard University Press, 1981. Cameron, Averil, and Stuart G. Hall. Eusebius: Life of Constantine. Oxford, UK: Clarendon, 1999. Durant, Will. Caesar and Christ, Vol. 3, The Story of Civilization. New York: Simon and Schuster, 1944. Ridley, Ronald T., ed. and trans. Zosimus: New History. Canberra: Australian Association for Byzantine Studies, 1982.

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