With Tiberius‘s departure, succession rested solely on Augustus‘ two young grandsons, Lucius and Gaius Caesar. The situation became more precarious in AD 2 with the death of Lucius. Augustus, with perhaps some pressure from Livia, allowed Tiberius to return to Rome as a private citizen and nothing more. In AD 4, Gaius was killed in Armenia, and Augustus had no other choice but to turn to Tiberius.
The death of Gaius in AD 4 initiated a flurry of activity in the household of Augustus. Tiberius was adopted as full son and heir and in turn, he was required to adopt his nephew, Germanicus, the son of his brother Drusus and Augustus’ niece Antonia Minor. Along with his adoption, Tiberius received tribunician power as well as a share of Augustus’s maius imperium, something that even Marcus Agrippa may never have had.
In AD 7, Agrippa Postumus, a younger brother of Gaius and Lucius, was disowned by Augustus and banished to the island of Pianosa, to live in solitary confinement.
Thus, when in AD 13, the powers held by Tiberius were made equal, rather than second, to Augustus’s own powers, he was for all intents and purposes a “co-princeps” with Augustus, and, in the event of the latter’s death, would simply continue to rule without an interregnum or possible upheaval.
However, according to Suetonius, after a two-year stint in Germania, which lasted from 10−12 AD, “Tiberius returned and celebrated the triumph which he had postponed, accompanied also by his generals, for whom he had obtained the triumphal regalia. And before turning to enter the Capitol, he dismounted from his chariot and fell at the knees of his father, who was presiding over the ceremonies.”
“Since the consuls caused a law to be passed soon after this that he should govern the provinces jointly with Augustus and hold the census with him, he set out for Illyricum on the conclusion of the lustral ceremonies.”
Thus, according to Suetonius, these ceremonies and the declaration of his “co-princeps” took place in the year 12 AD, after Tiberius’ return from Germania. “But he was at once recalled, and finding Augustus in his last illness but still alive, he spent an entire day with him in private.” Augustus died in AD 14, a month before his 76th birthday. He was buried with all due ceremony and, as had been arranged beforehand, deified, his will read, and Tiberius, now a middle aged man at 55, was confirmed as his sole surviving heir.
The Senate convened on 18 September, to validate Tiberius’s position as Princeps and, as it had done with Augustus before, extend the powers of the position to him. These proceedings are fully accounted by Tacitus. Tiberius already had the administrative and political powers of the Princeps, all he lacked were the titles—Augustus, Pater Patriae, and the Civic Crown (a crown made from laurel and oak, in honor of Augustus having saved the lives of Roman citizens).
Tiberius, however, attempted to play the same role as Augustus: that of the reluctant public servant who wants nothing more than to serve the state. This ended up throwing the entire affair into confusion, and rather than humble, he came across as derisive; rather than seeming to want to serve the state, he seemed obstructive. He cited his age as a reason why he could not act as Princeps, stated he did not wish the position, and then proceeded to ask for only a section of the state. Tiberius finally relented and accepted the powers voted to him, though according to Tacitus and Suetonius he refused to bear the titles Pater Patriae, Imperator, and Augustus, and declined the most solid emblem of the Princeps, the Civic Crown and laurels.
This meeting seems to have set the tone for Tiberius’s entire rule. He seems to have wished for the Senate and the state to simply act without him and his direct orders were rather vague, inspiring debate more on what he actually meant than on passing his legislation. In his first few years, Tiberius seemed to have wanted the Senate to act on its own, rather than as a servant to his will as it had been under Augustus. According to Tacitus, Tiberius derided the Senate as “men fit to be slaves.”