Lucius Aelius Sejanus (; – 18 October AD 31) was a Roman soldier and confidant of the Roman Emperor Tiberius. Of the Equites class by birth, Sejanus rose to power as prefect of the Praetorian Guard, the imperial bodyguard, of which he was commander from AD 14 until his execution for treason in AD 31.
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. When Tiberius withdrew to Capri in AD 26, Sejanus was left in control of the administration of the empire. For a time the most influential and feared citizen of Rome, Sejanus suddenly fell from power in AD 31, the year his career culminated with the consulship. Amidst suspicions of conspiracy against Tiberius, Sejanus was arrested and executed, along with his followers.
Family Sejanus was born around 20 BC at Volsinii, Etruria, into the Seia gens. His father was Lucius Seius Strabo.Tacitus, Annals IV.1 The Seii were Romans of the Equites class (or knights), the second-highest social class of the Roman Republic and the early Roman Empire. 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.
Strabo married into equally illustrious families. One of his wives was Cosconia Gallita, sister of Servius Cornelius Lentulus Maluginensis (suffect consul in AD 10) and Publius Cornelius Lentulus Scipio (suffect consul in AD 2). Sejanus was once thought to have possibly been a child of this marriage, but Ronald Syme has argued that Sejanus's mother was Junia Blaesa, sister of Junius Blaesus.
Sejanus's brother Lucius Seius Tubero, who became suffect consul in AD 18, was thought to have been a paternal half-brother, from his father Strabo marrying a daughter of Quintus Aelius Tubero but Syme has rejected this, instead he believes that Lucius Seius Tubero was Junia Blaesa's son from a marriage to Quintus Aelius Tubero whom Strabo adopted upon marrying Junia.
Sejanus was later adopted into the Aelia gens, possibly by Gaius Aelius Gallus the prefect, or Sextus Aelius Catus his half-brother's half-brother, and by Roman custom became known as Lucius Aelius Seianus or simply as Seianus.
The adoptive family of Sejanus counted two consuls among their ranks: Quintus Aelius Tubero (consul in 11 BC) and Sextus Aelius Catus (consul in AD 4), who was the father of Aelia Paetina, the second wife of the future Emperor Claudius. 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.Tacitus, Annals III.72, III.73
According to the ancient historian Tacitus, Sejanus was also a former favourite of the wealthy Marcus Gavius Apicius, whose daughter may have been Sejanus's first wife Apicata. With Apicata, Sejanus had two sons, Strabo and Capito Aelianus, and a daughter, Junilla.Tacitus, Annals IV.3
Rise to power
Praetorian prefect It is likely that Sejanus's father Strabo came to the attention of Augustus through his father's connection with Maecenas. Sometime after 2 BC,According to the Bingham dissertation, while the Guard had been formally established by Augustus in 27 BC, the first prefects were not appointed until 2 BC. See Bingham, p. 39. Strabo was appointed prefect of the Praetorian Guard, one of the two most powerful positions a Roman knight could attain in the Empire. This office he carried on dutifully and without incident until the death of Augustus in AD 14. 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. Upon the accession of Tiberius in AD 14, Sejanus was appointed prefect of the Praetorian Guard as the colleague of his father Strabo, and began his rise to prominence.
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.Bingham, p. 30. Much more than a guard however, the Praetorians also managed the day-to-day care of the city, such as general security and civil administration.Bingham, p. 238. Furthermore, their presence served as a constant reminder to the people and the Senate of the substantial armed force which served as the basis for the imperial power.Bingham, p. 232. 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.Bingham, pp. 231, 40.
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.Cassius Dio, Roman History LVII.19Bingham, p. 43. In AD 20 the scattered encampments inside the city were centralized into a single garrison just outside RomeTacitus, Annals IV.2Syme believes Tacitus delayed mention of these reforms until the year 23 for stylistic reasons. The actual date the Castra Praetoria was founded may have been AD 20. See and the number of cohorts was increased from nine to twelve,Bingham, p. 50. one of which now held the daily guard at the palace. The practice of joint leadership between two prefects was abandoned, and Sejanus himself appointed the centurions and tribunes. With these changes in effect, Sejanus now commanded the complete loyalty of a force of around 12,000 soldiers, all of which were at his immediate disposal. The facade of Augustus was no longer maintained, and Tiberius openly displayed the strength of the guard at parades.Cassius Dio, Roman History LVII.22
Feud with Drusus
In his capacity as Praetorian prefect, Sejanus quickly became a trusted advisor to Tiberius. By AD 23, he exerted a considerable influence over the decisions of the emperor, who referred to Sejanus as "Socius Laborum" (my partner in my toils). By this time, he had been raised to the rank of praetor, a position not normally granted to Romans of the equestrian class. A statue had been erected in his honor in the Theatre of Pompey and in the Senate his followers were advanced to public offices and governorships.Seneca the Younger, Essays, To Marcia On Consolation XXII.4–6 His privileged position caused resentment among the senatorial class and the imperial family, in particular earning him the enmity of Tiberius's son Drusus Julius Caesar.
The history of Sejanus and Drusus dated back to at least AD 15. That year a mutiny had broken out among legions posted in Pannonia and Germania. While his adopted son Germanicus restored order in Germania, Tiberius's biological son Drusus was sent to quell the uprising in Pannonia, accompanied by Sejanus and two Praetorian cohorts.Tacitus, Annals I.24 In part due to what the soldiers believed to be bad omens, Drusus quickly restored stability in the army and put the chief instigators to death publicly. The camp was purged of mutineers by the Praetorians and the legions returned to the winter barracks.Tacitus, Annals I.29, I.30 Despite this success, the following years witnessed a growing animosity between Drusus and Sejanus.
Since the death of Germanicus, Drusus had been groomed as the successor of his father, commanding legions in Illyricum in AD 18,Tacitus, Annals II.44, II.62 and sharing the consulship with Tiberius in AD 21.Tacitus, Annals III.31 In practice, Sejanus remained the second man in the empire, and was ambitious to expand his power. As early as AD 20, Sejanus had sought to solidify his connection with the imperial family by betrothing his daughter Junilla to the son of Claudius, Claudius Drusus.Tacitus, Annals III.29 At the time the girl was only 4 years old but the marriage never happened, as the boy mysteriously died a few days later of asphyxiation.Suetonius, The Lives of Twelve Caesars, Life of Claudius 27
When this failed, it seems Sejanus turned his attention toward eliminating Drusus. By AD 23 the enmity between the two men had reached a critical point. During an argument, Drusus had struck the prefect with his fist and openly lamented that "a stranger was invited to assist in the government while the emperor's son was alive".Tacitus, Annals IV.7 As Tiberius was in his sixties, the possibility of Drusus succeeding him in the near future loomed large. To secure his position, Sejanus plotted against Drusus and seduced his wife Livilla. Later, some (including Tiberius) suspected Sejanus to have fathered two of Livilla's children, Tiberius Gemellus and Germanicus Gemellus. With her as an accomplice, Drusus was slowly poisoned and died of seemingly natural causes on September 13, AD 23.Tacitus, Annals IV.8
Consolidation of power
The loss of his son was a major blow to Tiberius, personally and politically. 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.Tacitus, Annals III.56 With these hopes now dashed, Tiberius left his administration more than ever in the care of Sejanus and looked toward the sons of Germanicus (Nero Caesar, Drusus Caesar, and Caligula) as possible heirs.
Germanicus had died in AD 19, in somewhat suspicious circumstances in Syria.Tacitus, Annals II.72 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. Her relations with Tiberius became increasingly fraught, as she made it clear that she believed that he was responsible for the death of Germanicus.Tacitus, Annals IV.52, IV.53, IV.54 The climate was further poisoned by the hatred that Tiberius's mother Livia Drusilla (the widow of Augustus) felt for her, since Agrippina's ambition, to be the mother of emperors and thus Rome's first woman, was an open secret.Tacitus, Annals IV.12 Sejanus saw Agrippina's sons Nero, Drusus, and Caligula as a threat to his power.
Sejanus again attempted to marry into the Julio-Claudian family. Having divorced Apicata two years earlier, in AD 25 he asked to marry Drusus' widow Livilla, possibly with an eye towards placing himself, as an adopted Julian, in the position of a potential successor.Tacitus, Annals IV.39 The emperor denied this request, warning Sejanus that he was in danger of overstepping his rank.Tacitus, Annals IV.40 Alarmed by this sudden denigration, Sejanus changed his plans and began to isolate Tiberius from Rome. By fueling his paranoia towards Agrippina and the Senate, he induced the emperor to withdraw to the countryside of Campania, which he did in AD 26, and finally to the island of Capri, where he lived until his death in AD 37.Tacitus, Annals IV.57, IV.67 Sejanus easily controlled all information that passed between Tiberius (guarded by the Praetorians) and the capital.Tacitus, Annals IV.41