350–353 Late period The Battle of Mursa was fought on 28 September 351 between the eastern Roman armies led by the Emperor Constantius II and the western forces supporting the usurper Magnentius.

[8] This massacre precipitated a re-divisioning of the empire, by which Constantine took Gaul, Hispania, and Britain, while Constans acquired Italy, Africa, Dacia, and Illyricum, and Constantius inherited Asia, Egypt, and Syria.

[9] After attempting to impose his authority over Carthage and being blocked, Constantine II attacked his brother Constans in 340, but was ambushed and killed near Aquileia in northern Italy.

[11] Magnentius quickly marched his army into Italy, appointing Fabius Titanius as praefectus urbi consolidating his influence over Rome.

[11] Magnentius initially attempted a political dialogue with Constantius and Vetranio, but the rebellion of Nepotianus in Rome changed his intentions from joining the Constantian dynasty to supplanting it.

Crawford states the barbarian contingents took the lion's share of the casualties,[4] and yet the losses suffered at Mursa, according to Eutropius, could have won triumphs from foreign wars and brought peace.