Although he was born to Marcus Vipsanius Agrippa and Julia, Augustus' only daughter, Gaius and Lucius were raised by their grandfather as his adopted sons and joint-heirs.

[2] In 1 BC, Gaius was given command of the eastern provinces, after which he concluded a peace treaty with King Phraates V of Parthia on an island in the Euphrates.

In 4 AD, following the deaths of Gaius and Lucius, Augustus adopted his stepson, Tiberius, as well as his sole-surviving grandson, Agrippa Postumus.

Marcus Vipsanius Agrippa was an early supporter of Augustus (then "Octavius") during the Final War of the Roman Republic that ensued as a result of the assassination of Julius Caesar in 44 BC.

He was a key general in Augustus' armies, commanding troops in pivotal battles against Mark Antony and Sextus Pompeius.

Agrippa acted as tribune in the Senate to pass important legislation and, though he lacked some of the emperor's power and authority, he was approaching the position of co-regent.

Augustus taught Gaius and Lucius how to read, swim, and the other elements of education, taking special pains to train them to imitate his own handwriting, mostly by himself.

[18] Their father was no longer available to assume the reins of power if the Emperor were to die, and Augustus had to make it clear who his intended heirs were in case anything should happen.

[19] Gaius was elected consul designatus by the Comitia Centuriata in 6 BC with the intention that he should assume the consulship in his twentieth year.

[20][21] Roman support for the young prince soon spread through Italy;[22] statues and inscriptions were set up in every district to commemorate the fact that he had been nominated as a consul at an unprecedented age of fourteen.

[23][24] The following year (5 BC), when he attained military age, he assumed the toga virilis, and was introduced by Augustus to the Senate, who declared him as princeps iuventutis ("leader of the youth") and sevir turmae (commander of a cavalry division).

[26][27] The cities of Judaea rose in revolt after the procurator, Sabinus, garrisoned Syria Palaestina to guard the tens of millions of sesterces promised to the Emperor.

[29] Historian Ferrero speculates that Phraates may have been hoping to use Armenia as a bargaining chip to secure the release of his sons who were held captive by the Romans.

Having settled matters in Judaea, the Emperor decided to deploy an army to Armenia to re-establish its status as a Roman protectorate and to show the eastern world that Rome held dominion over all land as far as the Euphrates.

Gaius made a good choice because his presence represented that of the imperial family – all orders, promises, or threats coming from him were as valid as if they came from the Emperor himself.

[31] Before leaving for the east, he and his brother Lucius were given the authority to consecrate buildings, and they did, with their management of the games held to celebrate the dedication of the Temple of Mars Ultor (1 August 2 BC).

The Emperor entrusted Gaius with proconsular authority and had him marry his second cousin Livilla, the daughter of Drusus the Elder and Antonia Minor.

[42] The next year, on 1 January, he entered the consulship in absentia with his brother-in-law, Lucius Aemilius Paullus, in accordance with the decision of 6 BC which named him consul designate.

[21] Gaius, who was twenty, had reached Asia, and was probably at Antioch at the time his consulship commenced, where he was organizing an army for the invasion of Armenia and opening negotiations with Phraates in the hopes of securing an agreement.

[43] His inexperience meant he was forced to rely on his companions, namely the unruly Lollius, who had taken advantage of the powers he held, and was reportedly holding towns, individuals, and even sovereign princes for ransom.

[32][45] In the second half of the year,[46] Gaius had advanced with his army to the Parthian frontier to an unknown spot and brought Phraates to a final agreement on the proposals, in which he renounced all claims to Armenia and all power over his half-brothers.

[47] It was about this time that Augustus passed through Judea and commended Gaius for not offering prayers at Jerusalem, as it would have been provocative to the Jews living there.

It is known that the Nabataean Kingdom later became the province of Arabia, and so, it might be that Gaius conducted his "Arabian expedition" to either support or to discipline the King of Nabataea, Aretas IV.

It was for the crime of extorting presents from kings (regnum muneribus) that Lollius lost the friendship of Gaius and drank poison.

Pliny says he amassed a fortune from his crimes and that, as a result, his granddaughter could afford to wear jewelry worth 40,000,000 sesterces, a considerable amount of money.

[32][58][55] By the next year, 3 AD, he was entirely prostrated by the effects of his wound, had resigned his command, and withdrawn to Syria from where he informed Augustus that he had no further desire to take part in public life.

At the age of twenty-three, the young man whom the Emperor considered his heir and sole hope of prosperity had abandoned his prospects of reputation and power in a wild fit of despair and fear.

[21] Many honors were heaped upon Gaius by citizens and city officials of the Empire, including Colonia Obsequens Iulia Pisana (Pisa), where it was decreed that proper rites must be observed by matrons to lament his passing.