According to Sidonius Apollinaris, Ricimer served under the magister militum Flavius Aetius alongside the comes domesticorum Majorian, whom he befriended. Historian Penny MacGeorge writes, "Majorian certainly, and Ricimer probably, had served under Aetius, and there may have been other elements to this connection, political, personal, and social, that would have brought them both close to the centers of political power." Nonetheless, a power vacuum was created in the Western Empire after the events of 454 and 455, which saw the consecutive murders of Aetius and of the Western Emperor Valentinian III, who had been responsible for the magister militum's assassination. After the assassinations, the Roman Senator Petronius Maximus proclaimed himself emperor. Petronius's reign lasted less than three months, as shortly before the Vandal sacking of Rome in 455, he too was murdered. After Rome's sack, the Visigothic King Theodoric II proclaimed Avitus as Emperor, the Roman military commander in Gaul. In return for Theodoric II's support, Avitus agreed to allow the Visigoths to enter Suevi-controlled Hispania. After being proclaimed the new emperor in 456, Avitus mounted a campaign into Italy but was defeated in the Po Valley. In the interim, Avitus had named the Visigoth Remistus as magister militum. Following the arrival of Avitus in Rome, Majorian gave his support, albeit reluctantly, to the new emperor. Avitus is subsequently thought to have appointed Ricimer as comes, a prominent military position, but this remains unclear and it is possible that Ricimer was comes before the elevation of Avitus. At this point, however, the Western Empire encompassed only the Italian Peninsula and portions of southern Gaul, a mere fraction of the territory held by imperial Rome in previous centuries. Ricimer, nonetheless, raised an army and navy from the Germanic mercenaries available to him and commenced campaigns directed against "barbarian" tribes in conflict with the empire. Ricimer achieved his first important victory in 456, when he defeated the Vandals in the Battle of Agrigentum and the Battle of Corsica. Although Priscus writes that Avitus had sent him to Sicily to engage the Vandals, Hydatius states Ricimer defeated the Vandals near Corsica. Vandal raids and civil disaffection—due in part to famine—proved problematic for Avitus. Not only was he never recognized as Emperor of the West by the eastern Emperor Marcian, Avitus found himself in an especially precarious position since disruptive events had hardly settled when Ricimer and Majorian rebelled against their former patron. The