After his long life Augustus was succeeded by his adopted son Tiberius. Tiberius is something of an enigma: he was not Augustus’s son, he was the son of Augustus’s second wife by her first husband. Augustus did not really want him to succeed but all his children died off before he did, and Tiberius was the only survivor. But Tiberius was competent, very competent. He had been a successful general and a good administrator, and when Augustus formally adopted him and marked him out as his chosen successor, he waited dutifully, proving himself a safe choice.
The death of Augustus was one of the crucial moments in the history of Rome: would Rome revert to being a democracy, or was rule by one man to become the norm? Tiberius acted swiftly and efficiently. A couple of potential rivals were put to death and he firmly assumed control of the army and the acquiescence of the senate.
But Tiberius was not a likeable character: he was dour and no one really liked him. Part of the trouble is that we now have a first class history – that of Tacitus. Tacitus wrote at the end of the first and the beginning of the second century. But he began his Annals with the death of Augustus and the accession of Tiberius, and although he was a great historian he had a savage knife, and he always pounced on any weakness, and it is not always clear how far these weaknesses were real and how far they were contemporary gossip.
The reign of Tiberius tends to be dominated by the story of Sejanus, the Prefect of the Praetorian Guard, who may or may not have attempted to carry out a coup d’état. The Praetorian Guard was an invention of Augustus. If you are an emperor, you need a body guard, while in any case the capital city needs a police force to keep order. Therefore in 27 BC he selected an elite force nine cohorts strong (and a cohort is 1,000 soldiers) to form his Praetorian Guard. However Augustus was cautious and he kept this guard scattered in lodgings throughout the city. However when Tiberius took over, the Prefect of the Guard was one of the equites (knights) called Strabo and his ambitious young son Sejanus. Sejanus was ambitious and when his father went off to govern Egypt he persuaded Tiberius to gather the Praetorians together in a camp on the outskirts of the city, and to increase the number from nine cohorts to twelve. This meant that the guard was a major force of power.
Tiberius by this time was in his 60s, at an age when men wish to retire, and Sejanus had persuaded him to move to the south, at first to Campania, around Naples, and then to the island of Capri where he neglected the affairs of state and spent his time swimming with little boys. Sejanus became in effect the Emperor and he abused his power. Drusus, who was Tiberius’s designated successor, died in suspicious circumstances, it was said poisoned by Sejanus. Eventually Tiberius realised he must act. However action was difficult as Sejanus controlled the main force, that is the Praetorian Guard – 12,000 elite soldiers. Tiberius showed immense skill and cunning, sending contradictory and misleading letters to the senate and sending a small group of assassins to arrest Sejanus. It was a master class in how to deal with a coup d’état. Sejanus was arrested, condemned by the senate, and executed the same evening. Hence forward there were two prefects of the Praetorian Guard, and ensuring the loyalty of the Praetorians was always the first essential of any emperor.
Whether Sejanus really was planning a coup d’état was never absolutely certain, but the affair marked a change in Tiberius’personality. He retired to his villa in Capri, where he neglected the affairs of state, and went swimming with little boys whom he called his fishes, who came up behind him and nibbled him while he floated. Rumours abounded, and when he eventually died, the senators gave a sigh of relief.