Julio-Claudian dynasty
Tiberius

On 19 August AD 14, Augustus died. Tiberius had already been established as Princeps in all but name, and his position as heir was confirmed in Augustus' will.

Despite his difficult relationship with the Senate, Tiberius' first years were generally good. He stayed true to Augustus's plans for the succession and favoured his adopted son and nephew Germanicus over his natural son, Drusus, as did the Roman populace. On Tiberius' request, Germanicus was granted proconsular power and assumed command in the prime military zone of Germania, where he suppressed the mutiny there and led the formerly restless legions on campaigns against Germanic tribes from AD 14 to 16. Germanicus died in Syria in AD 19 and, on his deathbed, accused the governor of Syria, Gnaeus Calpurnius Piso, of murdering him at Tiberius's orders. With Germanicus dead, Tiberius began elevating his own son Drusus to replace him as the Imperial successor. By this time Tiberius had left more of the day-to-day running of the Empire to Lucius Aelius Sejanus.

Sejanus created an atmosphere of fear in Rome, controlling a network of informers and spies whose incentive to accuse others of treason was a share in the accused's property after their conviction and death. Treason trials became commonplace; few members of the Roman aristocracy were safe. The trials played up to Tiberius' growing paranoia, which made him more reliant on Sejanus, as well as allowing Sejanus to eliminate potential rivals. Victims of this reign of terror related to the imperial family included Gaius Asinius Gallus Saloninus, second husband of Tiberius' first wife Vipsania, who had since died, and Decimus Haterius Agrippa, grandson of Agrippa and husband of Augustus' great-niece.

Tiberius, perhaps sensitive to this ambition, rejected Sejanus's initial proposal to marry Livilla, Germanicus' sister and the widow of Tiberius' son Drusus the Younger, who had since died, in AD 25, but later had withdrawn his objections so that, in AD 30, Sejanus was betrothed to Julia Livia, daughter of Livilla and Drusus the Younger. Sejanus' family connection to the Imperial house was now imminent, and in AD 31 Sejanus held the Consulship with the emperor as his colleague, an honour Tiberius reserved only for heirs to the throne. When he was summoned to a meeting of the Senate later that year on 18 October AD 31, he probably expected to receive a share of the tribunician power. Instead, however, Tiberius' letter to the Senate, completely unexpectedly, requested the destruction of Sejanus and his faction. A purge followed, in which Sejanus and his most prominent supporters were killed. With Drusus dead and having had Germanicus' elder two sons Nero and Drusus convicted of treason and killed, along with their mother Agrippina, Tiberius appointed Caligula, Germanicus' youngest son, and Tiberius Gemellus, the son of Drusus the Younger and grandson of Tiberius, co-heirs. Drusus III's wife Aemilia Lepida was later forced to commit suicide after being accused of adultery.

Rome's second Emperor died at the port town of Misenum on 16 March AD 37, at the age of 78 years, having reigned for 23 years. Suetonius writes that the Prefect of the Praetorian Guard Naevius Sutorius Macro smothered Tiberius with a pillow to hasten Caligula's accession. According to Suetonius, he was known for his cruelty and debauchery through his perversion on the island of Capri where he forced young boys and girls into orgies. On one account when one of the boys complained, Tiberius had his legs broken.
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