Battle of Mons Seleucus


The Battle of Mons Seleucus was fought in 353 between the forces of the Roman emperor Constantius II and the forces of the usurper Magnentius. Constantius' forces were victorious, and Magnentius later committed suicide.

Background

Following his defeat at Mursa, Magnentius fled to Aquileia. Once there, in an attempt to ensure loyalty, he unleashed a campaign of terror throughout all of Gaul. This campaign included summoning all those loyal to him to support him in Aquileia. Decentius, brother of Magnentius and newly made Caesar, was engaged with an incursion of Alemanni, and was unable to lend his army to support Magnentius.
Constantius was in no position to press his advantage due to the heavy casualties his army had suffered at the Battle of Mursa Major. He therefore spent his time recruiting troops and retaking towns occupied by Magnentius. In the summer of 352, Constantius moved into Italy, only to find that Magnentius had chosen not to defend the peninsula. Following this, Constantius declared a general amnesty, which brought a fleet from Italy to his side.

Battle

The armies met at Mons Seleucus, in what is now La Bâtie-Montsaléon in Hautes-Alpes, south-eastern France. Constantius was again victorious and Magnentius took his own life on 10 August 353. Following his conclusive battle, Constantius wintered his troops at Arles.

Aftermath

Constantius, now undisputed Emperor of the Roman Empire, appointed Julian Caesar over the western half of the Empire in 355/6, and instigated a campaign to persecute those that had supported Magnentius. According to Ammianus Marcellinus, Constantius' notarii and his bodyguards needed only mere suspicion to inflict punishment and that Constantius became more "cruel, violent, and suspicious with age".