Early life (42BC-6BC)
Tiberius was born in Rome on 16 November 42 BC to Tiberius Claudius Nero and Livia. In 39 BC his mother divorced his biological father and, though again pregnant by Tiberius Nero, married Gaius Julius Caesar Octavianus. In 38 BC his brother, Nero Claudius Drusus, was born.
Little is recorded of Tiberius' early life. In 32 BC Tiberius, at the age of nine, delivered the eulogy for his biological father at the rostra. In 29 BC, he rode in the triumphal chariot along with his adoptive father Octavian in celebration of the defeat of Antony and Cleopatra at Actium.
In 23 BC Emperor Augustus became gravely ill, and his possible death threatened to plunge the Roman world into chaos again. Historians generally agree that it is during this time that the question of Augustus' heir became most acute, and while Augustus had seemed to indicate that Agrippa and Marcellus would carry on his position in the event of his death, the ambiguity of succession became Augustus' chief problem.
In response, a series of potential heirs seem to have been selected, among them Tiberius and his brother Drusus. In 24 BC, at the age of seventeen, Tiberius entered politics under Augustus' direction, receiving the position of quaestor, and was granted the right to stand for election as praetor and consul five years in advance of the age required by law. Similar provisions were made for Drusus.
Civil and military career
Shortly thereafter Tiberius began appearing in court as an advocate, and it was presumably at this time that his interest in Greek rhetoric began. In 20 BC, Tiberius was sent east under Marcus Vipsanius Agrippa. The Parthian Empire had captured the standards of the legions under the command of Marcus Licinius Crassus (53 BC) (at the Battle of Carrhae), Decidius Saxa (40 BC), and Mark Antony (36 BC).
After a year of negotiation, Tiberius led a sizable force into Armenia, presumably with the goal of establishing it as a Roman client state and ending the threat it posed on the Roman-Parthian border. Augustus was able to reach a compromise whereby the standards were returned, and Armenia remained a neutral territory between the two powers.
Tiberius married Vipsania Agrippina, the daughter of Augustus' close friend and greatest general, Marcus Vipsanius Agrippa. He was appointed to the position of praetor, and was sent with his legions to assist his brother Drusus in campaigns in the west. While Drusus focused his forces in Gallia Narbonensis and along the German frontier, Tiberius combated the tribes in the Alps and within Transalpine Gaul, conquering Raetia. In 15 BC he discovered the sources of the Danube, and soon afterward the bend of the middle course. Returning to Rome in 13 BC, Tiberius was appointed as consul, and around this same time his son, Drusus Julius Caesar, was born.
Agrippa's death in 12 BC elevated Tiberius and Drusus with respect to the succession. At Augustus' request in 11 BC, Tiberius divorced Vipsania and married Julia the Elder, Augustus' daughter and Agrippa's widow. Tiberius was very reluctant to do this, as Julia had made advances to him when she was married and Tiberius was happily married. His new marriage with Julia was happy at first, but turned sour.
Reportedly, Tiberius once ran into Vipsania again, and proceeded to follow her home crying and begging forgiveness; soon afterwards, Tiberius met with Augustus, and steps were taken to ensure that Tiberius and Vipsania would never meet again. Tiberius continued to be elevated by Augustus, and after Agrippa's death and his brother Drusus' death in 9 BC, seemed the clear candidate for succession. As such, in 12 BC he received military commissions in Pannonia and Germania; both areas highly volatile and of key importance to Augustan policy.
In 6 BC, Tiberius launched a pincer movement against the Marcomanni. Setting out northwest from Carnuntum on the Danube with four legions, Tiberius passed through Quadi territory in order to invade Marcomanni territory from the east. Meanwhile, general Gaius Sentius Saturninus would depart east from Moguntiacum on the Rhine with two or three legions, pass through newly annexed Hermunduri territory, and attack the Marcomanni from the west. The campaign was a resounding success, but Tiberius could not subjugate the Marcomanni because he was soon summoned to the Rhine frontier to protect Rome's new conquests in Germania.
He returned to Rome and was consul for a second time in 7 BC, and in 6 BC was granted tribunician power (tribunicia potestas) and control in the East, all of which mirrored positions that Agrippa had previously held. However, despite these successes and despite his advancement, Tiberius was not happy.