Maximus failed to obtain troops from the Visigoths and he fled as the Vandals arrived, became detached from his retinue and bodyguard in the confusion, and was killed by fellow Romans.

The invasion and sacking of Rome by the Vandals underlined the growing vulnerability of the Western Roman Empire, which would ultimately culminate in its collapse in 476.

[12] From 28 August 439 to 14 March 441, Maximus held the praetorian prefecture of Italy, the most important administrative and judicial non-imperial position in the Western Empire, and succeeded in that office by Anicius Acilius Glabrio Faustus.

[12] According to the historian John of Antioch,[17] Maximus poisoned the mind of the Emperor against Aëtius, resulting in the murder of his rival at the hands of Valentinian III.

Although Maximus swore revenge, he was equally motivated by ambition to supplant "a detested and despicable rival",[18] so he decided to move against Valentinian.

[9] He therefore allied himself with a eunuch of Valentinian's, the primicerius sacri cubiculi Heraclius, who had long opposed the general, with the hope of exercising more power over the emperor.

He chose as accomplices Optilia and Thraustila, two Scythians who had fought under the command of Aetius and who, after the death of their general, had been appointed as Valentinian's escort.

[9] Maximus easily convinced them that Valentinian was the only one responsible for the death of Aetius, and that the two soldiers must avenge their old commander, while at the same time also promising them a reward for the betrayal of the Emperor.

In particular, the army's support was split among three main candidates:[9] Maximianus, the former domesticus (bodyguard) of Aëtius, who was the son of an Egyptian merchant named Domninus who had become rich in Italy; the future emperor Majorian, who commanded the army after the death of Aetius and who had the backing of the Empress Licinia Eudoxia; and Maximus himself, who had the support of the Roman Senate and who secured the throne on 17 March by distributing money to the officials of the imperial palace.

[9] After gaining control of the royal palace, Maximus consolidated his hold on power by immediately marrying Licinia Eudoxia, the widow of Valentinian.

[20] She married him reluctantly, suspecting that he had been involved in the murder of her late husband; and indeed Maximus treated Valentinian III's assassins with considerable favour.

To further secure his position Maximus quickly appointed Avitus as magister militum and sent him on a mission to Toulouse to gain the support of the Visigoths.

[9] As Maximus rode out of the city on his own on 31 May 455, he was set upon by an angry mob, which stoned him to death (another account has it that he was killed by "a certain Roman soldier named Ursus").

Amidst the pillaging and looting of the city, and in response to the pleas of Pope Leo I, the Vandals are said to have refrained from arson, torture, and murder.

The Vandals also shipped many boatloads of Romans to North Africa as slaves, destroyed works of art and killed a number of citizens.