Battle of Mursa Major

The Battle of Mursa Major was fought in AD 351 between the eastern Roman armies led by Constantius II and the western forces supporting the usurper Magnentius.

The action took place somewhere along the valley of the Drava River, a Danube tributary in present-day Croatia.

Before the battle, Constantius sent Flavius Philippus, his Praetorian prefect, to negotiate with Magnentius, requiring that the usurper withdraw back to Gaul. After this inconclusive mission, one of Magnentius' commanders, the Frankish Claudius Silvanus, and most of his men deserted to Constantius, thus helping seal the outcome.

The battle was one of the bloodiest in Roman military history. According to Zonaras (xiii 8.17), Magnentius lost upwards of two-thirds of his troops, and Constantius about half of his army, for a total of well over 50,000 casualties, this at a time when the Empire was under severe external pressure from invading Goths, Alamanni and Persians, as well as internal dissensions and rebellions.

There was also a religious meaning to the conflict. Magnentius had restored some rights to the pagans, while Constantius even left the battlefield to pray on the nearby tomb of a Christian martyr. The bishop of Mursa, Valens, told the pious Emperor that an angel had reported to him the news of the victory, thus ending any chance of a pagan revival.

Magnentius, who had lost in the battle his most loyal supporter magister officiorum Marcellinus, would suffer another, final defeat, two years later at Mons Seleucus.