Agrippa Postumus was the youngest son of Marcus Vipsanius Agrippa and Julia the Elder, the daughter and only biological child of the Roman Emperor Augustus. Augustus initially considered Postumus as a potential successor and formally adopted him as his heir.
In AD 6, an uprising began in the Roman province of Illyricum. Augustus sent Tiberius to crush the revolt with his army, and after a year of delayed results, he sent Germanicus in his capacity as quaestor to assist in bringing the war to a swift end. The reason, Dio says, that Germanicus was chosen over Postumus is because Postumus was of an “illiberal nature”.
Postumus was known for being brutish, insolent, stubborn, and potentially violent. He possessed great physical strength and reportedly showed little interest in anything other than fishing. He resisted all efforts to improve his behavior, forcing Augustus to “abdicate” him from the Julii in AD 6 and banish him to a villa at Surrentum, near Pompeii. As an abdicated adoptee (adoptatus abdicatus) he lost the Julian name and returned to the gens Vipsania. The ancient historian Velleius Paterculus had this to say of the banishment:
About this time Agrippa…alienated from himself the affection of his father who was also his grandfather, falling into reckless ways by an amazing depravity of attitude and intellect; and soon, as his vices increased daily, he met the end which his madness deserved.
The following year, Augustus had the Senate make Postumus’ banishment permanent and had him moved to Planasia, a small island between Italy and Corsica. Augustus bolstered the natural inaccessibility of the rocky island by having an armed guard installed there. The Senate was ordered to never allow his release.
No consensus has emerged as to why Augustus banished Postumus in AD 7. Tacitus suggests that Augustus’ wife Livia had always disliked and shunned Postumus, as he stood in the way of her son Tiberius succeeding to power after Augustus, given that Postumus was a direct biological descendant of Augustus and Tiberius was not. Some modern historians theorise that Postumus may have become involved in a conspiracy against Augustus. Alternatively, it has been speculated that Postumus may have had learning difficulties. Postumus was held under intense security.
Augustus made no effort to contact Postumus until AD 14. In the summer of that year, Augustus left Rome, never to see the capital again. The main ancient sources of information about this period, Tacitus and Cassius Dio, suggest that Augustus left Rome in the company of only one trusted friend, the senator Paullus Fabius Maximus. The two left for Planasia to pay Augustus’ banished grandson a highly controversial visit.
Fabius and then Augustus himself died on their return, without revealing what they had been doing. There was much gossip over the outcome of their expedition. Tacitus recounts the rumor that Augustus had decided to reverse his decision and make Postumus his successor. In his account, Fabius indiscreetly told his wife what had occurred during the trip, and it cost him his life. Augustus’ wife Livia, too, was said to have poisoned her husband in order to prevent Postumus becoming the successor and thus supplanting her son Tiberius. While modern historians agree that such stories are highly unlikely, there is evidence that Augustus’ journey was historical. “It is the last act in Augustus’ long marathon of finding and keeping an heir to the new Empire“.
Augustus died on 19 August AD 14. Despite being banished, Postumus had not legally been disinherited, and so could claim a share in Augustus’ inheritance. According to Augustus’ will, sealed on 3 April AD 13, Tiberius would inherit two-thirds of his estate, and Livia one-third. There is no mention of Postumus in the document. Tiberius gave the eulogy at Augustus’ funeral and made a show of reluctantly accepting the title of princeps.
At almost the same time as Augustus’ death, Postumus was killed by centurion Gaius Sallustius Crispus, the great-nephew and adopted son of the historian Sallust. When Crispus reported to Tiberius that “his orders have been carried out”, Tiberius threatened to bring the matter before the Senate, professing that he had given no such orders. Tiberius denied any involvement, arguing that he had been en route to Illyricum when he was recalled to Rome, and later issued a statement that it was his father who gave the order that Agrippa Postumus not survive him. It is not clear if the killing was carried out before or after Tiberius became emperor.