Battle of Mursa Major in 351 AD


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Mar 8, 2013
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Battle of Mursa Major in 351 AD – History and War (

After the conquest of Illyria during 2nd and 1st century BC, Tiberius organized the province of Illyricum in last decade BC (from around 11 BC). Rebellion however flared up as a result of forced recruitment during the Marcommanic Wars, starting in 6 AD and lasting until 9 AD when rebels surrendered. Illyricum was consequently divided into Pannonia and Dalmatia, while Pannonia itself was divided into Eastern (Pannonia Inferior) and Western (Pannonia Superior) parts. During the Marcommanic Wars, Mursa served as a base for Legio X. Inscriptions also mention the Legio II Advitrix and Cohors I Ulpia Tracum, likely in passing on their way to the campaign zone during Hadrian’s rule.

Early on, Pannonia Superior was under jurisdiction of a consular legate commanding three legions, while Pannonia Inferior was given to a praetorian legate commanding a single legion. After Caracalla joined Brigetium to Pannonia Inferior, both provinces are of the same rank, commanded by consular legates with two legions each. Important military fortresses are established at Batina (Ad Militare), Zmajevac (Ad Nova), Dalj (Teutoburgium), along with multiple road outposts including the one at Osijek (Mursa).

During Flavian rule, Pannonia is romanized, urbanized, and Danube limes built. Vespasian transferred military camps from Drava to Danube, while permanent limes castels were built by Hadrian. Vespasian founded the colonies of Siscia and Sirmium, and Siscia becomes a base for the Pannonian fleet (classis Flavia Pannonica). Hadrian gave Mursa the status of colony or maybe even founded it, as indicated by the (now destroyed) inscription which read DIVO / HADRIANO / MURSENSES / CONDITORI / SVO (“to divine Hadrian, their founder – Mursians).

During the second half of the second century, Mursa serves as a temporary headquarters of the imperial procurator. It also served as a basis for a division of the Danubian fleet, while powerful ground forces were likely present due to continual Sarmatian threat. In 88 and 89 AD, legions XIV Gemina and XXV Rapax were transferred from Germany to Mursa. Latter was destroyed at some point, and replaced by the legion II Auditrix.

Massive barbarian incursion which happened during the rule of Marcus Aurelius and his son Commodus, Marcus Aurelius founds new forts at Danube and reinforces the Danubian fleet. He also settled Celtic Cotines around Mursa and Cibalium. Mursa itself was devastated during the wars, and majority of operations were carried out in the Pannonia Inferior. After Marcus Aurelius’ death, Emperor Commodus signed peace with Marcommanes, who had to provide several thousand soldiers, abandon the Danube area, return prisoners and accept Roman supervisors.

Column of Marcus Aurelius depicting Marcommanic Wars

Column of Marcus Aurelius depicting Marcommanic Wars

During the late Empire, Pannonian limes is under major pressure from barbarians. Emperor Gallienus defeated usurper Ingenuus near Mursa. Goths invaded Pannonia during Claudius II, while Aurelian had to repel Vandals in 270. Emperor Diocletian had to fight in Pannonia multiple times to repel Sarmatians, and eventually reorganized Pannonia into four provinces (Savia, Prima, Seconda, Valeria). These four provinces were grouped into diocese of Pannonia, with headquarters in Sirmium.

After Constantine the Great’s death, his sons divided the Empire. Constantine II and Constans soon came to blows, and Constantine II was killed in a battle near Aquileia. Constantius II took over the East, while West was ruled by Constans. Constans himself was killed by usurper Magnentius in 350., who then took over Italy, Gaul and Africa. Illyricum was taken over by old but successful general Vetranio. In 351., Constantius II and Magnentius clashed near Mursa, where Magnentius was defeated; Vetranio had already abdicated.

Battle of Mursa

Leadup to Battle

Third and Fourth Centuries are a time of numerous conflicts within the Roman Empire. Battle of Mursa itself solved one such conflict, one between the Emperor Constantius II and the usurper Magnentius. However, it also had major negative impact on the ability of the Empire to defend itself.

On 18th January 350, a group of conspirators led by the comes rei privatae Marcelin chose comes rei militaris Magnus Magnentius for an Emperor. Western Emperor Constans heard about the rebellion and attempted to escape to Hispania, but was captured in northern Pyrenees near fort Helena, and executed. Constans’ own unpopularity allowed Magnentius to quickly secure his power in Gaul, Hispania and Britain as well as North Africa. By the end of February his troops had conquered Italy as well, while he himself marched for Illyricum. While this was happening, Constans’ brother Constantius II – the Emperor of the East – was fighting against Persians at Euphrates. But Magnentius’ plans were thrown into disarray by the usurpation in Illyricum in March 350.

Bust of Emperor Magnentius, one of emperors who conflicted in the Battle of Mursa

Bust of the Emperor Magnentius (Flavius Magnus Magnentius, circa 303-353 A.D.), imperial age, marble 4th Century A.D., France, Vienne, Musee Lapidaire (Archaeological Museum), Gallo-Roman art

There, commander of the infantry (magister peditum per Illyricum) Vetranio accepted the purple at the request of Constantina, Constantius’ sister, who sought protection from Magnentius. Constantius, whom Constantina had informed of this, sent Vetranio an imperial diadem. Vetranio was recognized as an Emperor also by Magnentius, who was currently unprepared for a major conflict. Vetranio was likely also supported by Vulcacius Rufinus, Constans’ praetorian prefect for Illyricum, and also a member of Constantinian dynasty. Magnentius’ operations were further delayed by the events in Italy. In June 350., Julius Nepotianus – son of Eutropia, half-sister of Constantine I – rebelled in Rome, but after 28 days he was defeated and executed by Magnentius’ magister officiorum Marcellinus, while his mother Eutropia and possibly some other members of the Imperial family were also killed.

Magnentius’ attempts to seduce Vetranio were also blocked by Constantius’ return from the East. It is important to note also Vetranio’s coinage, which was minted with either Constantius’ name or his own. Coinage minted with Vetranio’s name bore inscriptions CONCORDIA MILITVM and VIRTVS AVGVSTORVM. These inscriptions – meaning “military unity” and “virtues of Augusts” respectively – prove that Vetranio carried out his actions in accord with the house of Constantine, possibly even Constantius himself.

In the East, Constantius had repelled persian king Shapur II., and had returned to Europe on 25th of December. On the same day he met Vetranio in Naissus, with the latter abdicating his throne and retiring to Bythinia. His troops joined the Constantius’ army, who spent winter reinforcing his position. Constantius declared his cousin Claudius Gallus (more often known as Constantius Gallus) a Caesar, with capital set up in Antioch. Magnentius responded by declaring his own cousin Decentius a Caesar.

Preparing for war, Magnentius imposed heavy taxes across the West, pulled troops from the Rhine and conscripted Franks and Saxons, thus leaving the Gaul essentially defenceless. Even when ready however he refused to attack, possibly due to uncertainty as to Constantius’ true strength – which now included Vetranio’s troops as well. In early summer of 351., Constantius moved on to the offensive from Sirmium, attempting to enter Italy. However, his vanguard was ambushed in the outer reaches of fortified region Claustra Alpium Iuliarum, specifically in passes near Atranto (now Trojana in Slovenia), and he was forced to retreat.

Magnentius and Constantius alike refused the peace offers they sent to each other, and in August 351. Magnentius stormed Siscia. Following this battle, Constantius made camp at Cibalia, while Magnentius unsuccessfully besieged Sirmium. After the failed siege, Magnentius moved to besiege Mursa, forcing Constantius to assist the city. Just before the battle, Frank Silvanus defected to Constantine with a unit of cavalry.

Battle of Mursa

Magnentius attempted to burn the iron-covered city doors, but failed. After learning of Constantius’ approach to Mursa, Magnentius decided to set up another ambush, and placed four Germanic auxilliary units inside the amphitheatre located just outside Mursa’s city walls. This move was noticed by defenders of Mursa, who reported it to Constantius. Constantius’ tribunes Scudilo and Manad took heavy infantry and archers, surrounded the amphitheatre, and slaughtered the enemy troops inside.

Majority of both armies arrayed in the battle order in the plains near Mursa, with Constantius having numerical advantage with 80 000 troops against Magnentius’ 36 000. This allowed Constantius to place his troops in a much wider formation. Both armies had one flank – Constantius’ right and Magnentius’ left – against Drava. Cavalry was on flanks, while archers and slingers were in the rear.

Battle started in the late afternoon, and lasted late into the night. Early in the battle, Constantius’ cavalry succeeded in breaking Magnentius’ weaker right wing and push it into the center, thus disordering Magnentius’ entire order of battle. Magnentius, who had taken up position on the right wing, was nearly captured and opted to flee, with his commander of cavalry Romulus taking over the command. Despite the breakdown in command and control, Magnentius’ troops continued to resist until late in the night, when Constantius’ cataphracts cut down Magnentius’ Germans.

Large number of Magnentius’ solders had drowned in Drava, and his camp was also captured. Of Magnentius high-ranking commanders, magister equitum Romulus had died, as likely had magister officiorum Marcellinus. Emperor Constantius guaranteed full pardon to remaining Magnentius’ troops, likely due to a large number of casualties on both sides – Magnentius had lost 24 000 troops, and Constantius 30 000. But while Constantius still had some 50 000 troops left, Magnentius had lost 2/3 of his field army.


Constantius’ propaganda presented the battle as a turning point in the war against Magnentius, and compared it with Constantine’s victory at the Milvian bridge, down to using the same symbolism of visions of Christ before the battle. Magnentius himself fled to Aquileia, and then to Gaul. There he was defeated again, at Mons Seleucus, and committed suicide on 10th August 353.

Battle had caused significant casualties, which had major negative impact on combat capability of the Roman army.

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