MAGNENTIUS, a Roman emperor of the west, was of barbarian extraction, and rose to the dignity of count under the Emperor Constantine. He afterwards entered the service of Constans; and in A.D. 350, while commanding the troops that defended the banks of the Rhine, he conceived the design of wresting the sceptre from that feeble and indolent prince. With the connivance of Marcellinus, Count of the Sacred Largesses, his plot was matured and carried into execution. That dignitary invited the officers of the army, then stationed near the city of Autun, to a feast in honour of the birthday of his son, and at a late hour of the banquet introduced Magnentius arrayed in the robes and insignia of royalty. The cry of "Long live Augustus" that was raised at this signal by several conspirators, was taken up unconsciously by the excited and astonished guests; and Magnentius forthwith took possession of the imperial palace at Autun. The assassination of Constans followed immediately; and within a short time Gaul, Italy, and the greater part of the western provinces had acknowledged the title of the usurper. After raising a formidable
army, Magnentius first attempted, but without success, to negotiate an agreement with Constantine, Emperor of the East, who was already intent upon revenging the death of his brother Constans. He then marched through Italy and Noricum into Pannonia, and in A.D. 351 repulsed the troops of Constantine on the plain of Sciscia. In the same year a battle fought before the town of Mursa, on the Drave, ended in the total defeat of Magnentius. A second routing of his forces in the defiles of the Cottian Alps completed his disaster; and when on the eve of being captured by his enemies, he died by his own hand at Lugdunum, in August A.D. 353.