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Final years

The affair of Sejanus and the final years of treason trials permanently damaged Tiberius's image and reputation. After Sejanus's fall, Tiberius's withdrawal from Rome was complete; the empire continued to run under the inertia of the bureaucracy established by Augustus, rather than through the leadership of the Princeps. Suetonius records that he became paranoid, and spent a great deal of time brooding over the death of his son. During this period there was a short invasion by Parthia, and incursions on Roman territories by Dacian and Germanic tribes.

Little was done to plan or secure Tiberius's succession. The Julians and their supporters were diminished in numbers and political influence, thanks to Sejanus, and Tiberius's immediate heirs were dead. Caligula, the sole surviving son of Germanicus, or Tiberius's own grandson, Tiberius Gemellus, were possibly candidates. However, Tiberius only made a half-hearted attempt at the end of his life to make Caligula a quaestor, and thus give him some credibility as a possible successor, while Gemellus himself was still only a teenager and thus completely unsuitable for some years to come.