Chapter XXV.—Of the Usurpers Magnentius and Vetranio.
About this time an extraordinary commotion shook the whole state, of the principal heads, of which we shall give a brief account, deeming it necessary not to pass over them altogether. We mentioned in our first book, 339 that after the death of the founder of Constantinople, his three sons succeeded him in the empire: it must now be also stated, that a kinsman of theirs, Dalmatius, so named from his father, shared with them the imperial authority. This person after being associated with them in the sovereignty for a very little while, the soldiers put to death, 340 Constantius having neither commanded his destruction, nor forbidden it. The manner in which Constantine the younger was also killed by the soldiers, on his invading that division of the empire which belonged to his brother, has already been recorded 341 more than once. After his death, the Persian war was raised against the Romans, in which Constantius did nothing prosperously: for in a battle fought by night on the frontiers of both parties, the Persians had to some slight extent the advantage. And this at a time when the affairs of the Christians became no less unsettled, there being great disturbance throughout the churches on account of Athanasius, and the term homoousion. Affairs having reached this pass, there sprang up a tyrant in the western parts called Magnentius, 342 who by treachery slew Constans, the emperor of the western division of the empire, at that time residing in the Gauls. This being done, a furious civil war arose, and Magnentius made himself master of all Italy, reduced Africa and Libya under his power, and even obtained possession of the Gauls. But at the city of Sirmium in Illyricum, the military set up another tyrant whose name was Vetranio; 343 while a fresh trouble threw Rome itself into commotion. For there was a nephew of Constantines, Nepotian by name, who, supported by a body of gladiators, there assumed the sovereignty. He was, however, slain by some of the officers of Magnentius, who himself invaded the western provinces, and spread desolation in every direction.
The same account is given by Eunap. X. 9, and by Zosimus, II. 40.53:341
Ch. 5, above.53:342
Magnentius was governor of the provinces of Rhœtia, and assassinated Constans, as above. Cf. Zosimus, II. 43.53:343
This whole affair is treated extensively in Zosimus, II. 43–48.