The Battle of Arelate was fought in 458 near Arelate (Arles) between Western Roman Emperor Majorian and Visigothic king Theodoric II. After the assassination of Flavius Aetius in 454, the Visigoths began to expand their kingdom at the expense of the crumbling Roman administration in Gaul and Hispania. When Majorian became emperor in 457, the Visigoths under king Theodoric II had just recently defeated the Suebic Kingdom in north-west Hispania and were consolidating their hold on the rest of the peninsula.
After defeating a Vandal attack on Italy, Majorian launched a campaign against the Visigothic Kingdom in southern Gaul. Defeating king Theodoric II at the Battle of Arelate, Majorian forced the Goths to abandon their possessions in Septimania and Hispania and return to federate status immediately. Majorian then attacked the Burgundian Kingdom, defeating them at the Siege of Lugdunum, expelling them from the Rhone valley and reducing them to federate status.
In late 458, Majorian entered Gaul, with an army strengthened by barbarian units. The Emperor personally led the army, leaving Ricimer in Italy and choosing Aegidius and the magister militiae Nepotianus as collaborators. The imperial army defeated the Visigoths under king Theodoric II at the Battle of Arelate, forcing the Visigoths to abandon Septimania and withdraw west to Aquitania. The Roman victory was decisive: under the new treaty the Visigoths had to relinquish their vast conquests in Hispania and return to federate status. Majorian chose his trusted general Aegidius as the new magister militum per Gallias (military commander of Gaul) and sent an envoy to Hispania, to report the victory over the Visigoths and the new treaty with Theodoric II.
Theoderic II, son of Theodoric I, obtained the throne by killing his elder brother Thorismund. The English historian Edward Gibbon writes that "he justified this atrocious deed by the design which his predecessor had formed of violating his alliance with the empire." In late 458 the Western Roman Emperor, Majorian entered Septimania to attack Theodoric and reclaim the province for the empire. Majorian defeated Theodoric at the Battle of Arelate, forcing the Visigoths to abandon Septimania and withdraw west to Aquitania. Under the new treaty with the Romans, the Visigoths had to relinquish their recent conquests in Hispania and return to federate status. However, after the assassination of Majorian in 461, Theodoric recaptured Septimania and invaded Hispania again. Theodoric was himself murdered in 466 by his younger brother Euric, who succeeded him to the throne.
Aegidius was born in Gaul, a province of the Western Roman Empire. It is believed that he came from the aristocratic Syagrii family, based upon the name of his son, Syagrius. While this evidence is not absolute, modern historians consider a connection to the family likely, by birth or marriage. Aegidius served under Aetius during the latter's time as magister militum (master of soldiers) of the Western Roman Empire. He also served alongside the future emperor Majorian. Aegidius was either a founding member of Majorian and Ricimer's faction, or else he quickly joined it. After Majorian became Western Roman Emperor, Aegidius was granted the title of magister militum per Gallias (master of the soldiers for Gaul) in 458, as a reward for his loyalty. In the same year, Aegidius led troops at the Battle of Arelate, against the Visigoths under King Theodoric II. Aegidius is credited by ancient sources as being the primary cause for Theodoric II's defeat. As a result of the battle, Theodoric II was forced to return Visigoth territory in Hispania to the Western Roman Empire, and submit again to being a Roman vassal.