Aegidius

Before his ascension he was an ardent supporter of the Western Roman emperor Majorian, who appointed him magister militum per Gallias ("Master of the Soldiers for Gaul") in 458.

After the general Ricimer assassinated Majorian and replaced him with Emperor Libius Severus, Aegidius rebelled and began governing his Gallic territory as an independent kingdom.

He may have pledged his allegiance to the Eastern Roman emperor Leo I. Aegidius repeatedly threatened to invade Italy and dethrone Libius Severus, but never actually launched such an invasion; historians have suggested he was unwilling to launch an invasion due to the pressure of the Visigoths, or else because it would leave Gaul exposed.

[3] After Majorian became Western Roman emperor, Aegidius was granted the title magister militum per Gallias in 458 as a reward for his loyalty.

[2][3] The Ripuarian Franks conquered Cologne and Trier from the Romans c. 457, and Aegidius was besieged in Arles by the Visigoths under King Theodoric II for a time in 457/458,[4] before Majorian defeated him.

[5] In the same year, Aegidius led troops at the Battle of Arelate against the Visigoths,[6] where he is credited by ancient sources as being the primary cause for Theodoric II's defeat.

Aegidius may have pledged his allegiance directly to Leo I in order to legitimize his independence from the Western Roman Empire, and his retention of the Gallic legions.

Modern historian Penny MacGeorge has suggested that this was due to pressure from the Visigoths, whereas others assert that he was unable or unwilling to march to Italy, leaving Gaul exposed.

[3] It is known that during this time, Ricimer ceded Lyons to the Burgundians, and Narbonne and most of Narbonensis Prima to the Visigoths, in exchange for alliances.

The two people most likely to have been given the title of magister militum per Gallias (master of soldiers in Gaul) were the Roman general Agrippinus, whom Aegidius had previously accused of treason, or the Burgundian King Gundioc, who was Ricimer's brother-in-law.

[15] According to a story known to Gregory of Tours and the Chronicle of Fredegar, the Frankish King Childeric I, who controlled much of northern Gaul, was exiled at some point after 457, and the Franks then elected Aegidius to rule them.

[3][18] Michael Kulikowski posits that his comitatenses (armies) were so heavily Frankish at this point, that he could fairly be remembered as a king, rather than general.

The loss of Cologne and Trier is provided by the Liber Historiae Francorum, and his encirclement in Arles by Paulinus of Périgueux's Life of St. Martin and Gregory.