Europe 353: Battle of Mons Seleucus
After his defeat at Mursa Major, Magnentius fled to Italy and then to Gaul. In 353 Constantius II crossed the Alps into southern Gaul, where he defeated his opponent at Mons Seleucus in July. With nowhere left to run, Magnentius committed suicide at Lugdunum (Lyon) the following month.
352–353 Fall of Magnentian Italy▲
In the summer of 352 Constantius II invaded Italy, bypassing Magnentius’ fortifications at Aquileia via a mountain path. Outmaneuvered by his adversary, and with Rome in revolt, Magnentius checked his pursuers at Ticinum then hurriedly withdrew across the Alps to Gaul. By late September Constantius was firmly in control of Italy and from there he sent fleets to establish his authority in Africa and Spain.
352 Constantius II’s Second Sarmatian Campaign▲
In the summer of 353, just as Constantius II was leading his army into Italy in pursuit of Magnentius, the Sarmatians suddenly rose up against Roman authority to his rear. The emperor was forced to turn back east with a significant force to suppress this uprising before resuming the war against Magnentius.
352?–353 Constantius Gallus’ Isaurian War▲
In the early 350s the Isaurians rose up in the Taurus mountains and began a campaign of banditry in Cilicia, Lycaonia, and Pamphylia. After destroying a number of ships and raiding many towns, they besieged the city of Seleucia (Silifke) in around 353. However, just as Seleucia was approaching famine, the Isaurians learned that Constantius Gallus had dispatched a large force to deal with them and, abandoning their efforts, dispersed into the mountains.
352–353 Chnodomar vs Decentius▲
In 352 Constantius II encouraged the Germanic Rhine tribes to turn against Magnentius. That year King Chnodomar of the Alemanni crossed into Gaul, where he defeated Decentius, Magnentius’ brother and the Caesar of Gaul, in a pitched battle. The invaders then roamed freely across eastern Gaul, sacking many cities.
Jul–Aug 353 Poemenius▲
Sometime around early July 353 the legions at Augusta Treverorum (Trier), capital of the Praetorian Prefecture of Gaul, rose up against Magnentius and appointed an officer named Poemenius as their leader. Poemenius immediately began minting coins for Constantius II and repulsed Magnentius’ brother Decentius when he attempted to gain entry into the city. Learning of Magnentius’ death soon after, Decentius hanged himself at Agedincum (Sens) in mid-August, bringing an end to the Magnentian regime in Gaul.
3 Jul 353 Battle of Mons Seleucus▲
In the summer of 353 Constantius II crossed from Italy into Gaul to face the usurper Magnentius. Emerging through the Alps, he found his opponent’s army at Mons Seleucus (La Bâtie-Montsaléon) and decisively defeated him. Magnentius fled to Lugdunum (Lyon), where he took his own life by falling on his sword in early August.