Tiberius, having replaced Drusus in Germany and now the clear candidate for imperial succession, had returned to Rome and been elected consul for a second time in 7 BCE.

He is elevated in 6 BCE to a share in his stepfather's tribunician power and control in the East, all of which mirror positions held previously by the late Marcus Vipsanius Agrippa, the close friend, son-in-law and minister to Augustus.

Shortly afterward, on the verge of accepting command in the East and becoming the second most powerful man in Rome, Tiberius goes into retirement on the island of Rhodes.

This is attributed by some historians to jealousy of his stepnephew Gaius Caesar, adopted by Augustus in this year.

The promiscuous, and very public, behavior of his unhappily married wife, Julia, may have also played a part.

Indeed, Tacitus calls it Tiberius' intima causa, his innermost reason for departing for Rhodes, and seems to ascribe the entire move to a hatred of Julia and a longing for Vipsania, who he had divorced in obedience to the wishes of Augustus.

Tiberius has found himself married to a woman he loathes, who publicly humiliates him with nighttime escapades in the Forum, and forbidden to see the woman he had loved.

Whatever Tiberius's motives, the withdrawal is almost disastrous for Augustus's succession plans.

Gaius and Lucius are still in their early teens, and Augustus, now fifty-seven years old, has no immediate successor.

There is no longer a guarantee of a peaceful transfer of power after Augustus's death, nor a guarantee that his family, and therefore his family's allies, will continue to hold power should the position of princeps survive.

Somewhat apocryphal stories tell of Augustus pleading with Tiberius to stay, even going so far as to stage a serious illness.

Tiberius's response was to anchor off the shore of Ostia until word came that Augustus had survived, then sailing straightway for Rhodes.

With Tiberius's departure, succession rests solely on Augustus' two young grandsons, Lucius and Gaius Caesar.

The Roman plebs agitate for Gaius to be created consul, despite the fact that he is only 14 and has not yet assumed the toga virilis, a plain white toga worn on formal occasions by most Roman men of legal age, generally about fourteen to eighteen years, but it could be any stage in their teens.

The first wearing of the toga virilis is part of the celebrations on reaching maturity.

As a compromise, it is agreed that he should have the right to sit in the Senate House, and he was made consul designatus with the intention that he should assume the consulship in his twentieth year.

Gaius is at this point created "Prince of Youth" ("princeps iuventutis"), an honorific that makes him one of the symbolic heads of the equestrian order.