MAGNENTIUS (Flavius Magnus Magnentius), ROMAN EMPEROR. — Of barbarian, probably Germanic, origin, having risen to high rank in the army, he was induced by the foolish conduct of Constans, son of Constantine, to usurp the purple in agreement with the comes sacrarum largitionum Marcellinus. Constans was killed, and M. was recognized as emperor in Gaul, Spain, and Africa (350).
But the wisest and most astute of Constantine’s three sons, Constantius II, could neither recognize his brother’s killer nor tolerate the separation of all the western provinces from the rest of the Empire, especially since other usurpers were arising in Illyricum and at Rome. He therefore prepared for war, which, moreover, the impulsive M. had made inevitable, advancing into Illyricum and the Balkan Peninsula. M. was defeated near Mursa (Osijek), but managed to flee and take refuge in Aquileia, whence, as a result of Constantius’ exceedingly slow advance, he proceeded to Gaul. Defeated once more at Mons Seleucus (La Batie Neuve), he shut himself up in Lugdunum, where, being uncertain of the loyalty of his men, he killed himself in Aug. 353.