The Battle of the Milvian Bridge

by Dugit

The Rise and Decline of Diocletian’s Tetrarchy

Between the years of 235 and 284 AD, Rome was ruled by no less than 26 emperors, but then, a soldier from Illyricum called Diocletian, seized power from Numerian (perpetuating the eternal pattern), but kept it. Diocletian proceeded to begin a series of lengthy reforms that would breathe a few more years of life into the parched imperial shell. He introduced a tetrarchy, with each of the rulers administrating one of the empire’s praefectures- Gaul (Gallica, Britannia, Hispania, and a section of Numidia), Italy (Italy, Sicily, Numidia, and Carthaginian Africa), Illyricum (Greece, Crete and Illyria), and The East (Thrace, Anatolia, Syria and Egypt). Each praefecture had a ruler, an Augustus, that was accompanied by an adopted heir, the Caesar. This measure was to assure the quashing of any legitimate future rebellions, but problems of struggles in lower Imperial ranks continued unabated. Diocletian ruled the two eastern quarters from Nicomedia, and Maximian, his associate, ruled the two western quarters from Rome, both with their own Caesar (Galerius in the East and Constantius in the west), forming an effective administrative tetrarchy.

When Diocletian retired from Augustus in 305, Maximian followed suit. As expected, Galerius and Constantius rose to Augustus, but Constantius named Flavius Severus as Caesar in the west and Galerius named Maximinus Daia as Caesar in the east, which seemed quite a slap in the face to the eldest sons of Maximian and Constantius, Valerius Maxentius and Constantine respectively. When Constantius died in 306, Severus rose to Augustus, but troops in Gaul named Constantine as Augustus, as did the troops in Italy for Maxentius. Constantine declined the higher position of Augustus in the west, leaving that to Maxentius. When the civil war ended, Severus was executed and Maxentius ceded the title of Augustus to his father Maximian, who came out of retirement to reoccupy the imperial throne.

To add further confusion, Galerius refused to accept either Constantine or Maximian as western Augustus, instead naming one of his generals, Licinius, as western Augustus. Maxentius, during the invasion of the west, ousted his father from power, to take the position of Augustus himself. Daia fought Galerius for the title of Augustus in the east. Thus, six men held the position of Augustus originally intended for two, and yet the position of Caesar remained vacant. None of the men were willing to cede their positions, and none of them supported or even trusted each other. Diocletian called a meeting at Carnuntum and gave every man the title of Augustus (except Maximian who apparently proclaimed his permanent retirement from politics) of their own region of the empire. This mandate lasted a meager two years before strife arose once more. Maximian fled to Constantine’s court in Gaul from his son, but then attempted to overthrow his host. He was taken prisoner and allowed to kill himself for his trouble. When Galerius died, once more order was restored, as was the original idea of a tetrarchy, except all the rulers in the tetrarchy held the title of Augustus. Had Constantine ceded the title of Augustus to Maxentius alone, Maxentius probably would never have felt the greed to rule the entire western Roman Empire, and, to Constantine, declared war.

The Battle of Milvian Bridge

Constantine had long been contemplating this very situation, and had 100,000 troops under his control. However, more than half had to be left to keep order on the Germanic and British frontiers, leaving him with 40,000 under his control. Constantine began a march on Rome, whereupon Maxentius sent troops under a variety of generals; all were defeated at Susa, Turin and Milan, each victory for Constantine won in inferior numbers. As Constantine made it into Latium, he had circa 50,000 troops under his control, after defeating Maxentius’s best general (his magister militum), Pompeianus, at Brescia and Verona. Maxentius hid inside Rome, with a force of 75,000 (some sources state as much as 120,000), including the Praetorian Guard, who, unlike in many previous occasions were completely loyal to their emperor, as Maxentius had long been showering them with privileges to avoid the potential of assassination, as had been the case so many times in the past.

The events that occurred then are mainly stuff of legend, but are worthy of note. Maxentius consulted the Sybilline books, which roughly predicted that “Than on that day the enemy of Rome shall perish.” Convinced that Constantine was the enemy of Rome, he went to battle in good graces. He lead his army out of the Aurelian walls and onto a plain near the village of Saxa Rubra, with the River Tiber at his back. Constantine also received an omen. Primary sources state that he saw a flaming cross in the sky with the Greek words ‘en tutoi nika’- ‘with this sign conquer’ (some say ‘in hoc signo vinces’- Latin). The following morning (some say as a dream), he was instructed by a voice to adorn his soldiers’ shields with the Greek letters chi and rho together on his shields- ‘the symbol of Christus’. Many of his soldiers were Christian, but many others followed the cults of Mithras and the Unconquerable Sun- both used similar religious symbolism, so all of Constantine’s soldiers went into battle with good graces. Constantine vowed to turn Christian if he won the battle.

The two armies formed up on one side of the Tiber, with Maxentius’s back to the Tiber, and Constantine facing him. Both adopted the classic deployment method with the infantry core aligned in rows in the center, and with skirmishers at the front and the cavalry at the sides. Maxentius’s plans were very straightforward; he would simply engage the infantry center, and defeat both the cavalry wings and the infantry center due to his advantage in man-power. Constantine’s battle plan was unclear- it seems that he was ready to adhere to whatever his opponent proceeded to do.

At this stage in the Roman Empire, heavy infantry was still the prime bullwark of any Roman army, but did not resemble the legions of early Imperium. The helmet had been changed, as had the armor and weaponry. The sword was longer, and the heavy spears used before the charge had been lightened so more could be carried. They very closely resembled German soldiers, from where most of Rome’s recruits were coming. Spearmen were also employed at this stage to fend off the barbarian heavy cavalry that was proving increasingly effective; they were armed with the hoplite spear, or the cavalry sword- the spatha, which was longer than the standard gladius. Constantine did not have the large personal Praetorian guard that Maxentius had, but made good use of the Imperial Household Cavalry from administrative centers such as Trier. The battle began with a few minor skirmishes- Maxentius’s Italian javelinmen attacked first, and fought with Constantine’s Gallic light infantry. Neither army had a great proportion of archers, so the battle couldn’t really be won at a range. The skirmishes were inconclusive, and both contingents were forced back to their main army.

Constantine commanded one of the cavalry wings and lead the initial charge. His Gallic medium cavalry from Lugdunensis and Narbonensis was lighter and far more mobile than Maxentius’s Italian heavy cavalry, but the Gallics were heavier than Maxentius’s Mauretanian auxiliaries; both of Maxentius’s cavalry corps were crushed, leaving the heavy infantry core. Constantine’s Gallic legions pinned down Maxentius’s center, whilst the Gallic cavalry charged into the flanks.

They panicked, and only the Praetorian Guard remained steady, making a stubborn stand at the banks of the Tiber. Perhaps this was all they could do, as there was no escape whatsoever. They were overwhelmed and died where they stood, including Maxentius’s Praetorian Praefect. The rest of the infantry had but one escape route- the narrow Milvian Bridge to their backs.

The situation was so crowded and desperate, that not even Maxentius could get across. Constantine’s troops harassed the interlocked bundle on the Milvian Bridge, causing further casualties. He attempted to swim the Tiber, but drowned; his body was bought to surface the next day. The great casualties suffered by Maxentius stands as a testament to his poor planning before the battle; of how he ineptly deployed on the far side of the bridge, and did not allow much room to manoeuvre, or to place reserves for when they were needed. Constantine proceeded to annex Rome, and secured the Western Empire against any pro-Maxentius resistance.


After this victory, Constantine became devout Christian- he believed that God had given him the victory at Milvian Bridge, even though it was obvious he was a competent general. This was the event that began the mass Christianization of the Roman Empire.

Licinius, although he did not take a part in the battle, he played a great part in its aftermath. Licinius did not pursue his attack on the west, and instead fought and defeated Maximinus Daia for sole ruler of the east. Constantine and Licinius signed the Edict of Milan circa February 313, which dictated mutual religious tolerance (Constantine was devout Christian; Licinius was devout Pagan). However, things were not always well between the two. When Constantine defeated the stubborn Licinius in 314, Constantine robbed Licinius of almost all of Roman Europe. Licinius responded by persecuting Christians in the east. This inevitably set up Christiandom’s hate of Pagan worship for years to come. Licinius was eventually killed after his final defeat in 323.

This allowed Constantine to finish effectively what Diocletian had started. He established a second imperial capital at Byzantium, renaming it Constantinople in his honor. This set up the division of the empire into its two infamous halves. The east became prosperous and lasted for more than a millennium, whilst the west became increasingly poor, weak and under attack. The Roman realm in the west died officially only 150 years after the christening of Constantinople, when Romulus Augustulus, the last officially recognized western emperor (the Realm of Soissons, independent Roman Illyria (under Julius Nepos) and Romano-Britain after 476 are considered meager successor kingdoms) was deposed by a barbarian king of Italy, Odoacer the Vandal. The empire in the west had ceased to be.