Lucius Aelius Sejanus (Sejanus)

Lucius Aelius Sejanus (d. 31 AD) was a praetorian prefect of the Roman Empire, and for a time the most influential citizen of Rome.

Sejanus was appointed praetorian prefect on the accession of Tiberius, as the colleague of his father L. Seius Strabo. On his father's appointment to the governorship of Egypt, he became sole commander of the Praetorian Guard, and began to increase his power. After the death of Tiberius' son Drusus in 23, he consolidated his power over the Senate. Despite failing in an attempt to marry Drusus' widow in 25, which would make him part of the ruling house, he increased his power further upon Tiberius' retirement to Capri in 27.

In 31, when he gained the consulship, Sejanus felt his position was unassailable, and plotted to seize the purple for himself. Tiberius discovered the plot and had him executed. Macro succeeded him as commander of the Praetorian Guard.

Sejanus hailed from Volsinii in Etruria. He and his father shared the Praetorian Prefecture until A.D. 15 when the father, L. Seius Strabo, was promoted to be Prefect of Egypt, the pinnacle of an equestrian career under the Principate. Sejanus, now sole Prefect of the Guard, enjoyed powerful connections to senatorial houses and had been a companion to Gaius Caesar on his mission to the East, 1 B.C. - A.D. 4. Through a combination of energetic efficiency, fawning sycophancy, and outward displays of loyalty, he gained the position of Tiberius's closest friend and advisor. One development that favored Sejanus was the concentration of all nine cohorts of Praetorian Guardsmen into a single camp at Rome. Augustus had billeted these troops discretely in small towns around Rome, but now Tiberius -- undoubtedly with Sejanus's encouragement, perhaps even at his suggestion -- brought them into the city, probably in A.D. 17 or 18. Sejanus, therefore, commanded some 9,000 troops within the city limits. As Sejanus's public profile became more and more pronounced, his statues were erected in public places, and Tiberius openly praised him as "the partner of my labors." But Sejanus had his own ideas.

According to Tacitus, Sejanus's first subversive act was the seduction of Tiberius's daughter-in-law, Livilla, at the time married to Drusus, Tiberius's son. Drusus, it seems, resented Sejanus's influence over his father so the Prefect, in conjunction with Livilla, poisoned him in A.D. 23. There followed a series of attacks on Agrippina's friends, mostly played out in the courts in the guise of charges of treason (maiestas) but, in Tacitus's account, actually the work of Sejanus.

Then, in A.D. 25, Sejanus asked Tiberius for permission to marry Livilla, Drusus's widow. Tiberius refused. This setback for Sejanus was offset the following year, when the ageing emperor withdrew from Rome to live on Capri; he was never to return to the city. Tiberius was most probably encouraged in his decision to retire by Sejanus, who now became the chief vehicle of access to the emperor. With Tiberius absent, Sejanus vented his full fury against Agrippina's family, whose demise he had been plotting for some time. In rapid succession Agrippina and her eldest son, Nero Caesar, and eventually also Drusus Caesar, who had been involved in his brother's downfall, were arrested, convicted, and imprisoned. By A.D. 31 Sejanus had reached the pinnacle of his power and was effectively emperor himself. The sources paint a grimly comic picture of senators lining up to pay respects to a man they considered their social inferior.

What exactly Sejanus was aiming at remains a matter of intense debate. The Prefect's attacks against Agrippina and his proposal to marry Drusus's widow, Livilla, suggest that he was attempting to follow the precedent of Agrippa, that is, an outsider who became the emperor's successor through a combination of overt loyalty, necessity, and a family alliance forged by marriage. Tiberius, perhaps sensitive to this ambition, rejected Sejanus's initial proposal to marry Livilla in A.D. 25, but later put it about that he had withdrawn his objections so that, in A.D. 30., Sejanus was betrothed to Livilla's daughter (Tiberius' granddaughter). The Prefect's family connection to the Imperial house was now imminent. In A.D. 31 Sejanus held the consulship with the emperor as his colleague, an honor Tiberius reserved only for heirs to the throne. Further, when Sejanus surrendered the consulship early in the year, he was granted a share of the emperor's proconsular power. When he was summoned to a meeting of the Senate on 18 October in that year he probably expected to receive a share of the tribunician power; with that he would, after all, have become Tiberius's Agrippa.

But in a shocking and unexpected turn of events, the letter sent by Tiberius from Capri initially praised Sejanus extensively, and then suddenly denounced him as a traitor and demanded his arrest. Chaos ensued. Senators long allied with Sejanus headed for the exits, the others were confused -- was this a test of their loyalty? what did the emperor want them to do? -- but the Praetorian Guard, the very troops formerly under Sejanus's command but recently and secretly transferred to the command of Q. Sutorius Macro, arrested Sejanus, conveyed him to prison, and shortly afterwards executed him summarily. A witch-hunt followed. Sejanus's family was arrested and executed; Livilla perished; followers and friends of Sejanus were denounced and imprisoned, or tried and executed; some committed suicide. All around the city, grim scenes were played out, and as late as A.D. 33 a general massacre of all those still in custody took place.

Tiberius himself later claimed that he turned on Sejanus because he had been alerted to Sejanus's plot against Germanicus's family. This explanation has been rejected by most ancient and modern authorities, since Sejanus's demise did nothing to alleviate that family's troubles: Agrippina remained under house arrest, Drusus was still housed in the Palatine's basement, and both died violently within three years of the Prefect's fall. Tiberius is also said to have discovered Sejanus's part in his own son's death in A.D. 23; the source of this information, however, is suspect. Possibly, in the highly charged atmosphere surrounding Sejanus's fall, the news acted as a catalyst, but its truth cannot be verified. Whatever the precise reasons, Sejanus's career and demise, and that of those around him, was an object lesson in the dangers of imperial politics. To achieve power under the emperors, the ambitious needed to get close to the source, but getting too close could lead to catastrophe, for both the aspirant and any who rode his coattails.