MAGNUS MAXIMUS, a native of Spain, who had accompanied Theodosius on several expeditions and from 368 held high military rank in Britain. The disaffected troops having proclaimed Maximus emperor, he crossed over to Gaul, attacked Gratian (?..), and drove him from Paris to Lyons, where he was murdered by a partisan of Maximus. Theodosius being unable to avenge the death of his colleague, an agreement was made (384 or 385) by which Maximus was recognized as Augustus and sole emperor in Gaul, Spain and Britain, while Valentinian II. was to remain unmolested in Italy and Illyricum, Theodosius retaining his sovereignty in the East. In 387 Maximus crossed the Alps, Valentinian was speedily put to flight, while the invader established himself in Milan and for the time became master of Italy. Theodosius now took vigorous measures. Advancing with a powerful army, he twice defeated the troops of Maximus at Siscia on the Save, and at Poetovio on the Danube. He then hurried on to Aquileia, where Maximus had shut himself up, and had him beheaded. Under the name of Maxen Wledig, Maximus appears in the list of Welsh royal heroes (see R. Williams , Biog. Diet, of Eminent Welshmen, 1852; " The Dream of Maxen Wledig," in the Mabinogion).
Full account with classical references in H. Richter, Das westromische Reich, besonders unter den Kaisern Gratian, Valentinian II. und Maximus (1865); see also H. Schiller, Geschichte der romischen Kaiserzeit, ii. (1887); Gibbon, Decline and Fall, ch. 27; Tillemont, Hist, des empereurs, v.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)