While the Praetorian Guard was formally established under Emperor Augustus, Sejanus introduced a number of reforms which saw the unit evolve beyond a mere bodyguard into a powerful and influential branch of the government involved in public security, civil administration and ultimately political intercession; these changes had a lasting impact on the course of the Principate.

During the 20s, Sejanus gradually accumulated power by consolidating his influence over Tiberius and eliminating potential political opponents, including the emperor's son Drusus Julius Caesar.

Sejanus's grandfather maintained relations with senatorial families through his marriage with Terentia, a sister of the wife of Gaius Maecenas, who was one of Emperor Augustus' most powerful political allies.[3]: p.

Sejanus's uncle, Junius Blaesus, distinguished himself as a military commander; he became proconsul of Africa in AD 21 and earned triumphal honors by crushing the rebellion of Tacfarinas.

Little is known about the life Sejanus led prior to this date, but according to Tacitus, he accompanied Gaius Caesar, adopted son of Augustus, during his campaigns in Armenia in 1 BC.

The Praetorian Guard was an elite unit of the Roman army formed by Augustus in 27 BC, with the specific function to serve as a bodyguard to the emperor and members of the imperial family.

[11] Augustus was careful however to uphold the republican veneer of this regime, and only allowed nine cohorts to be formed (one fewer than in a normal Roman legion), which were inconspicuously scattered across various lodging houses in the city, and commanded by two prefects.

[12] When Strabo was assigned to the governorship of Egypt in AD 15, Sejanus became the sole commander of the Praetorians and instigated reforms that helped shape the guard into a powerful tool of the principate.

[13][14] In AD 20 the scattered encampments inside the city were centralized into a single garrison just outside Rome[15][16] and the number of cohorts was increased from nine to twelve,[17] one of which now held the daily guard at the palace.

[20] In part due to what the soldiers believed to be bad omens, Drusus quickly managed to restore stability in the army and publicly put the chief instigators to death.

Over the years he had grown increasingly disillusioned with the position of princeps, and by sharing the tribunician powers with Drusus in AD 22 he had prepared to relinquish some of his responsibilities in favour of his son.

[29] Following his death, his wife Agrippina the Elder returned to Rome with their six children and became increasingly involved with a group of senators who opposed the growing power of Sejanus.

Having divorced Apicata two years earlier, he asked to marry Drusus' widow Livilla in AD 25, possibly with an eye towards placing himself, as an adopted Julian, in the position of a potential successor.

[36] Sejanus began a series of purge trials of senators and wealthy equestrians in the city, removing those capable of opposing his power as well as extending the imperial (and his own) treasury.

What caused his downfall is unclear:[44] ancient historians disagree about the nature of his conspiracy, whether it was Tiberius or Sejanus who struck first and in which order subsequent events occurred.

According to Josephus, it was Antonia, the mother of Livilla, who finally alerted Tiberius to the growing threat Sejanus posed (possibly with information provided by Satrius Secundus), in a letter she dispatched to Capri in the care of her freedman Pallas.

At dawn, he entered the Senate; while the letter was being read, Macro assumed control of the Praetorian Guard, and members of the vigiles, led by Publius Graecinius Laco, surrounded the building.

[52] The senators at first congratulated Sejanus, but when the letter, which initially digressed into completely unrelated matters, suddenly denounced him and ordered his arrest, he was immediately apprehended and imprisoned in the Tullianum.

[54] Following the issue of damnatio memoriae by the Senate, Sejanus's statues were torn down and his name obliterated from all public records, even from coins, as in the one pictured opposite.

Edward Togo Salmon wrote that, In the whole twenty two years of Tiberius's reign, not more than fifty-two persons were accused of treason, of whom almost half escaped conviction, while the four innocent people to be condemned fell victims to the excessive zeal of the Senate, not to the Emperor's tyranny.

[64]The reforms of Sejanus most significantly included the founding of the Castra Praetoria, which established the Praetorian Guard as the powerful political force, for which it is primarily known today.

He was charged for having eulogized Marcus Junius Brutus and spoken of Gaius Cassius Longinus as the last of the true Romans, which was considered an offence under the Lex Maiestatis; the Senate ordered the burning of his writings.

[82] The prudent need for anonymity is suggested by the arrest of Sir John Eliot, who was sent to the Tower of London for his outspoken criticism of the Duke in the 1626 parliament, comparing him to Sejanus.

[83] Following Buckingham's death in 1628, when it was safer to do so, a translation of a history by Pierre Matthieu was published under the title, The Powerful Favourite, the life of Aelius Sejanus.

[84] This was followed in 1634 by another translation, Sir Thomas Hawkins' Politicall Observations upon the Fall of Sejanus, which had originally been titled Della peripetia di fortuna (Of Changes of Fortune) by its author, Giovanni Battista Manzini.

[85][86] Later in the century Anthony Ashley Cooper, 1st Earl of Shaftesbury, was the target of the four-page political pamphlet Sejanus, or The popular favourite, now in his solitude, and sufferings, signed with the pseudonym Timothy Tory (1681).

[87] The story of Sejanus, with reference to the Earl's imprisonment in the Tower on a charge of treason, is interpreted as an argument for absolute monarchy, direct rule without the intermediary of politicians.

This gives the clue of how to take what is to follow and consists of a conversation between Punch and the Hangman, opening with the question 'Is this same Sejanus to go out of the World like a Man, or to die the Death of a mad Dog?

[96] The first of these was Miles Gerald Keon's Dion and the Sibyls: A Classic Christian Novel (London, 1866);[97] later examples include Paul L. Maier's Pontius Pilate (Grand Rapids MI 1968)[98] and Chris Seepe's The Conspiracy to Assassinate Jesus Christ (Toronto 2012).

This was true of William Percival Crozier's historical romance The Fates Are Laughing (1945), which was written by a classicist with an eye for detail and set during the fall of Sejanus and the reign of Caligula.