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  • James Houser

October 28, 312 - The Battle of the Milvian Bridge

Updated: Jun 17, 2021

October 28, 312 AD. The Romans are in the middle of a civil war to determine who will rule the Empire, drink. But something is different this time. The leader of one faction has allegedly seen a vision in the sky commanding him to conquer under a certain sign, and urges his men to paint a forbidden symbol on their shields. His name is Constantine, and for the first time a Roman army will fight with the Christian cross on their shields. There is change in the air.


The Roman Empire had just emerged from the worst period in its history. From 235 to 284 AD, Rome had staggered under the weight of plagues, invasions, economic crisis, civil wars and societal collapse. The assassination of the Emperor Severus Alexander in 235 precipitated a period of constant turnover in leadership, during which there were 26 men who claimed to be Emperor at one point or another. Most of these were Roman generals, and the Empire essentially became a free-for-all: anyone who could muster something resembling an army might take Rome, declare himself Emperor, and get bowled over by the next guy with delusions of grandeur within a year or two. It was not a recipe for stable or effective leadership, and the Empire’s institutions and borders crumbled under the strain.


The Crisis of the Third Century, as it came to be known, more or less ended the Classical Rome we know from pop culture and paintings. The Roman Empire that emerged from the chaos would be a different animal altogether. It would be much more militarized, authoritarian, and East-oriented than the old beast. The terms Roman historians use to differentiate these two periods are the “Principate” and the “Dominate.” The Principate was the Empire that Augustus Caesar had founded: firmly based in the city of Rome, obeying the old political conventions and forms of the defunct Republic, with the military firmly in civilian (Imperial) control. The Empire that walked out of five decades of chaos in 284 was the Dominate: increasingly decentralized, ruled more and more by generals and bureaucracies, and increasingly Greek and Eastern in its outlook.


The man who solidified most of these changes was the defining personality of the Roman Empire’s last era as a political unit. He was the Emperor Diocletian, the man who came out on top after so many years of chaos. Diocletian had risen through the ranks of the Roman Army to fight his way to the Imperial title, and unlike so many of his predecessors he managed to actually keep it. His reorganizations, reforms, and firm rule stabilized the Empire for the first time in living memory, and his numerous military campaigns reestablished the Empire’s borders and drove back all its enemies. Diocletian ruled Rome for 19 years – but he did not rule alone.


The lesson Diocletian had taken from the Empire’s chaos was that the Roman realm had grown too large to be ruled by one person. The centrality of the city of Rome to the Empire, too, had a negative effect since petty city politics and the ambitions of low officials often compromised the Empire’s stability. An overcentralized realm was unable to respond to the multiple threats that Rome now faced. In order to overcome this issue, Diocletian established a new tradition of “co-emperors” within the Empire. No Emperor would rule alone from now on; instead, he would have partners.


Diocletian first appointed a fellow army officer named Maximian as his co-emperor (“Augustus”) in 286. Maximian’s job was to rule the West Roman Empire – Britain, France, Spain, North Africa, and Italy. Diocletian continued to rule the richer and more populous East Roman Empire – Greece, the Balkans, Turkey, Egypt, Syria and Palestine. Diocletian undoubtedly gave this job to Maximian because the guy wasn’t overly blessed with brains, and so posed a lesser risk than other people might have.


In 293, though, Diocletian went one step further in his process of delegation. Maybe even two Emperors wasn’t enough. So Diocletian and Maximian each appointed a deputy, called a “Caesar”, to play the subordinate role to their “Augustus.” They both adopted skilled generals as their new subordinates: Diocletian took on Galerius as his Caesar, while Maximian took on Constantius (!!! Important guy). This “Rule of Four” would define the final centuries of the Roman Empire’s existence as a unit with its increasing tendency towards decentralization.


Diocletian’s outlook was far more militaristic, bureaucratic and autocratic than his predecessors. The new capitals of Rome were in Nicomedia, Milan, Belgrade and Trier – border cities rather than big urban centers, the better from which to control the Roman Army. Increasing court ceremony and separation from the masses accompanied this change, and the growing depth and complexity of the Roman bureaucracy enabled a far sterner control of the state. It is an odd paradox that as Rome grew more decentralized, it grew more dictatorial, but that’s more or less what happened.


One of Diocletian’s policies proved less successful than the others, and that was his take on Christians. This strange little cult had grown increasingly prevalent in the Roman Empire, despite its official ban, and Diocletian frowned at the church spires visible from his palace in Nicomedia. The problem that Romans had with Christians was that, unlike any other religious group, Christians refused to sacrifice and make prayers for the Emperor. This wasn’t a problem for any other religion, but the Christian monotheism and the Commandment that “Thou shalt worship no other Gods before me” tended to put a whole damper on that Emperor-worship thing. Diocletian had never liked Christians, and when he started to view them as a disruptive influence, things got out of hand.


Diocletian was not a gentle man. His upbringing and his age did not foster a gentle nature. The whole “religious tolerance” thing was not one of his strong suits. In 303, some of the ritual sacrifices routinely held at the Roman court failed to produce a reading, and the priests blamed the undisturbed practices of the Christians as their main scapegoat. Diocletian seized on this excuse to get rid of the hated religious sect, and in February 303 issued his first “Edict Against the Christians,” banning Christian worship and ordering the destruction of churches across the Empire. What followed was a spree of executions, lynchings, mob violence and arson throughout the year.


Ultimately, though, Diocletian’s “Great Persecution” was unsuccessful, and failed to achieve its aim. The martyrdom of Christians and the reluctance of local officials to crack down on their own citizens only strengthened the rebellious faith, and helped to secure its ultimate triumph.


Strap in, it’s about to get complex. Lots of moving parts, and there’s no good way to explain this.


Diocletian stepped down in 305– peaceably! He happily retired to tend to his garden, confident that the system he had established would function in his absence. For good measure, he forced Maximian to – reluctantly - retire as well, paving the way for Constantius and Galerius to succeed their former bosses as the new Emperors of West and East. The big question now arose: who would succeed the newly rising Emperors in their old positions as Caesar? In the east, the answer was easy: Galerius appointed his nephew Maximinus Daia to the rank of Caesar. But there was a problem in the west, since both the old Augustus Maximian and the new Augustus Constantius had ambitious sons, both of whom had their eyes on the Western throne.


And now we introduce our chief rivals in today’s story. Maximian’s son Maxentius was a born schemer and sycophant, and because he had spent his whole life sucking up to Diocletian he was also a furious anti-Christian. Constantius’ son, on the other hand, was named Constantine – a charismatic young man who had the acclaim of the Roman army. Constantine’s mother was a Christian, and somehow this had flown under Diocletian’s radar; whatever his personal religious leanings early in life, Constantine was certainly more sympathetic to Christianity than the other ruling members of the Roman Empire.


But neither Maxentius nor Constantine was going to be Constantius’ new Caesar. Over both their objections, the Roman elites chose a guy named Severus as the new Caesar in the West. This ultimately was to prove the downfall of the Tetrarchy. The problem of decentralizing authority is that it creates a lot of room for a lot more people to be upset when they DON’T get jobs. You just have a lot more people who feel like they deserve power cut out of the loop, and this is never good for the stability of a system.


So with Constantine and Maxentius both outside the inner circles of power, the Roman Empire was cruising for a bruising when something happened. That something happened in 306 AD, only a year after Diocletian’s alleged retirement, when Emperor in the West Constantius died after only a year on the throne. A lot of things happened all at once. First, Constantius’s army in Britain proclaimed his beloved son Constantine as the new Emperor in the West. (The “Rule of Four” falling apart under literally the slightest sign of strain did not bode well.) Of course, Severus was supposed to become Emperor, since he was the Caesar, but he was away on other business. As soon as Constantine tried to claim the title, Maxentius said “If he’s doing it, why can’t I?” and also launched an uprising in Italy to claim the Imperial title. If this all wasn’t chaos enough, old Maximian (Maxentius’ father, try and keep up, I KNOW this is difficult) rolled out to try and reclaim the Imperial throne.



After a lot of maneuvering, plotting, and fighting that left Severus dead and every contender with his own angry army, Diocletian had to leave his quiet farm for one last hurrah to settle this whole business. In 308, all the disgruntled parties met for a conference in Austria. Some new guy named Licinus would become Augustus in the West, Constantine would become Caesar, Maxentius was left out in the cold again, and Maximian – look at me, Maximian – would retire and stay retired. Deal? Deal.


Yeah, so this is chaos plain and simple. There’s a lot of names floating around, plots, relationships, everything. Maybe I should just gloss over the next four years of murderous intrigue. Show of hands, who wants me to hit the fast forward button? One, two, three, okay the ayes have it. Fast forward, here we go.


So 311 rolls around and EVERYONE AND THEIR BROTHER are trying to be Emperor again. Constantine (our protagonist today) had set up in Gaul and Britain, while Maxentius ruled over Italy. Licinius governed the Balkans and Maximinus Daia in the east, but neither of those guys are important today so we’re going to pretend they don’t exist.


The problem with this whole situation was that no one could stand to play second fiddle to anyone else. Diocletian had tried to solve the Empire’s problems with his new system, but instead his new system had created a f***ing spiderweb of mayhem that even I (ME) cannot describe in a single Facebook post. If Constantine or Maxentius had accepted a secondary position as Caesar, then all this mess could have been avoided. But neither of them could, because both of them – as the sons of former Emperors in the West – thought they had a right to rule. So it would have to come to blows.


Maxentius had not made himself popular in Italy. He was something of a petty tyrant who spent lavishly on his palaces and his bodyguards while allowing public buildings to fall into disrepair and disarray while abusing the common people. Paranoid to an absurd amount even for this period in Roman history, he saw plots everywhere – and was especially wary of Constantine, his rival in the West who resided just over the Alps. Both Maxentius and Constantine continued to mint coins presenting themselves as the only Emperor of the Western Empire, an increasingly passive-aggressive form of machismo that only grew more pathetic over time. Finally, in 311 Maxentius began to prepare for an invasion of Gaul. He would be the only Emperor in the West if it killed him.


Constantine learned of Maxentius’ plans, and decided that he was going to strike first. He had 100,000 troops under his command, but most of those were required to guard Britain or Gaul from barbarian attacks. He ended up leading only 20,000 men across the melting snow of the Alpine passes into Italy in early 312. Maxentius sent various armies up to defeat his rival, each of which Constantine defeated. Constantine’s four major battlefield victories came against superior numbers. As he made his way south, slowly but surely, the charismatic young Christian-friendly emperor picked up recruits both from his defeated enemies and from the local population. Soon his army numbered about 40,000 men, even as Maxentius called out 75,000 for the final showdown.


As Constantine approached Rome, something…happened. What exactly happened is not quite clear to this day. His army drew near to Rome, even though they were outnumbered nearly two to one. Maxentius was prepared for a battle, approached the priestesses of the Roman cult for guidance; they predicted that on October 28, 312 AD, “the enemy of the Romans” would die. Satisfied, Maxentius went north to fight his nemesis. Constantine, though, had had a religious experience of his own.


According to the story, Constantine experienced a religious vision. In one version Constantine was allegedly commanded in a dream on the evening of October 27, the night before the battle, to “delineate the heavenly sign on the shields of his soldiers.” In the version of the historian Eusebius, who claimed to have heard the story from Constantine himself, the Emperor was marching with his army to the camp near Rome when he looked to the sun and saw a cross of light. Above it appeared the Greek words “in hoc signo vinces.” The literal translation of these words is something like “In this sign, conquer.” Either way, the message was clear: the symbol was the favorite sigil of that persecuted and ill-treated minority in the Roman Empire, the luckless Christians.


Whether or not he received a vision, or in what form, the result was certain. Constantine ordered his soldiers to paint a symbol on their shields: not an eagle, or an old Roman wolf’s head, but a mark called the labarum. This is the Christian cross as an “X”, with a “P” branching down the middle – a sigil derived from the Greek letters Chi (X) and Rho (P), for the first two Greek letters of the word “Christ.” This Chi-Rho symbol is still used as an Orthodox or Greek cross to this day. This was the symbol painted on the shields of Constantine’s Roman soldiers as they marched to battle on October 28, 312 A.D., to confront the army of Maxentius.


It is important to note how groundbreaking this was. The Roman state had had Christians among its citizens ever since…well, the age of Jesus. But this was the first time that any figure of Roman authority had extended so much as recognition to the insurgent religious movement. They could not have been more than 10% of the population. And here was Constantine, a claimant to the Roman Empire, not only openly acknowledging the Christians but painting their symbol on the shields of his soldiers. Undoubtedly there were Christians in his ranks, but this was probably also true of Maxentius’ army; at any rate, it is hard to see what advantage Constantine would really gain from acknowledging the Christian creed – unless, of course, he had some secret faith that he had hidden for years.


It is difficult, even today, to truly know whether Constantine was genuine in this move. There is reason to believe that his adoption of Christianity was a cynical ploy, a way to contrast himself with Maxentius. But again, this move probably alienated as many people as it won over, and Christians were not major movers or shakers in any part of the Empire. Most Christians, in fact, lived in the East – an area that neither Maxentius nor Constantine was remotely concerned about at this point in time. Constantine later told the bishop Eusebius that he vowed before the battle that if he was victorious, he would convert to Christianity; until now, he had been a follower of the Apollo cult in public. So as odd as it may seem, given how cynical I tend to be, I lean towards taking Constantine (mostly) at his word: he marched forward under the Chi-Rho because he was taking a gamble on faith in his mother’s religion.


Details of the Battle of the Milvian Bridge are sketchy. On October 28, 312 AD, Maxentius marched his army out of Rome and laid out his formation in front of the Milvian Bridge just north of the city, positioning his back to the river. The Milvian Bridge still stands today in the same site, albeit somewhat remodeled. If it needs to be said, putting your army’s back to the river is an EXTREMELY basic no-no in military tactics, since it gives them no way to escape if the battle goes badly and inhibits your flexibility. Maxentius had placed his troops SO close to the river that they had no room to maneuver or give ground if necessary. So this was already a dum-dum move from the get-go.


Constantine was already well-known as a skillful general at this point, and despite being grossly outnumbered his troops were somewhat inspired by their commander’s weird-ass, last-minute religious conversion and the new symbol on their shields. Constantine himself led his cavalry wing against Maxentius’ horsemen, and his more mobile Gallic troopers outmaneuvered and overran the heavier, less flexible Italian cavalry. Crushing both of his foe’s flanks, Constantine then ordered his infantry to advance. A general melee broke out between the heavy, chainmailed, sword-armed infantry of both sides until Constantine’s assault pushed their opponents back in a few places.


The problem was that there was nowhere to fall back TO. When any unit of Maxentius’ army had to give ground for any reason, they trekked backward into the water of the Tiber River, panicked, and ran for the Milvian Bridge. Though Maxentius’ infantry by and large fought well, the river at their backs made them panicky and claustrophobic, and soon all the infantry formations were disintegrating. Maxentius ordered a retreat, determined to make a stand at Rome itself, but the only escape route was over the bridge – and as the army flooded to cross it, retreat turned into rout and panic.


The Praetorian Guard, Maxentius’ bodyguards who had put him in power, made a valiant last stand on the Milvian Bridge but were finally overwhelmed and cut down to a man. Trying to push his way across the bridge, Maxentius was shoved over the side by his fleeing soldiers and disappeared into the river; dragged down by his glamorous armor. The would-be Emperor’s body was later found floating in the waters of the Tiber. He had not been slain; he had drowned.


The victory at the Milvian Bridge made Constantine the undisputed ruler of the West Roman Empire, and he entered Rome in triumph the next day with Maxentius’ head paraded through the streets. Notably, though, Constantine refused to take the traditional route of proceeding to the Temple of Jupiter in Rome’s center. This was an omission that did not go unnoticed by observers or historians; no Roman Emperor rising to power had refused to pay homage to Jupiter before. It was something that was just not done. But Constantine had made clear where his sympathies now lay: not with the gods, but with the God.


Only one year later, Constantine and the Eastern Emperor Licinius would together proclaim the Edict of Milan, granting Christianity freedom of worship for the first time in the history of the Roman Empire. Though Constantine was still hedging his bets – he did not openly declare himself Christian – it was clear what path he was on, and as his reign continued he became more and more supportive of Christianity. When Licinius renounced the Edict of Milan in 314 and began to persecute Christians again, he and Constantine came to blows, and in 324 Constantine reabsorbed the East Empire into his rule. For the first time since Diocletian’s victory way back in 283, the Roman Empire was under a single head.


Constantine’s total triumph, which began at the Milvian Bridge, led to Christianity becoming the dominant religion throughout the Roman Empire. Constantine was something like a “Diet Christian,” rarely following Christian rituals or expressing much depth of faith. He founded a new Roman capital at Constantinople, explicitly intended as a new “Christian” Rome, though this may have been a move to divorce himself from old Roman traditions. Though he interfered constantly in Christian religious disputes, this was more of an assertion of authority than an expression of religious doctrine.


Whatever his actual beliefs – we will never know – Constantine’s patronage and support of the Church saw a sea change in the Empire’s religious confessions. It was due to Constantine’s vision, or whatever happened that day before the Milvian Bridge, that Europe became Christian.


The fact that Christianity is the world’s largest religion today, rather than a forgotten minority faith of the ancient era, is a direct result of that mysterious event the day before the Battle of the Milvian Bridge.


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