Tiberius Caesar had the unenviable task of succeeding his stepfather Augustus. He would always be a pale shadow of the charismatic founder of the Roman Empire. Tiberius’s time in power was also scarred by the influence of Sejanus, the prefect of the emperor’s Praetorian Guard. Sejanus used Tiberius’s insecurity and reticence to rule and to seize a great deal of power. The relatively low-class general may even have considered seizing the imperial purple for himself. But his ambition would result in his execution, and the execution of many of Rome’s leading elites.
Family Ambition
Lucius Aelius Sejanus, better known today as just Sejanus, was an equite. This meant that he was born (in around 20 BCE) into the second highest class in Roman society, behind the aristocratic patricians. This suggests that his family was wealthy and well-off, but not among Rome’s highest social elite. But Sejanus’s family, the Seii, seem to have been social climbers and very well connected by the time Sejanus reached manhood.
Sejanus’s grandfather, from the Italian town of Volsinii, married very well when he matched with Terentia, the sister of Gaius Maecenus, one of the emperor Augustus’s most trusted allies. His son, Sejanus’s father, Lucius Seius Strabo married Cosconia Gallita, the sister of Publius Cornelius Lentulus Scipio, consul in 2 CE and a descendent of the famous Scipios of the Punic Wars. This paved the way for Sejanus’s older brother, Lucius Seius Tubero, to serve as consul alongside Germanicus, the adopted son and presumed heir of the emperor Tiberius Caesar, in 18 CE.
Meanwhile, Sejanus was adopted into the Aelia family by Gaius Aelius Gallus. This kind of adoption of adult men was a common practice to ensure the continuation of family names. The Aelia was a prestigious family that had already produced two consuls, including Sextus Aelius Catus, whose daughter, Aelia Paetina, would go on to be the second wife of Tiberius’s nephew, Claudius, whom no one suspected would later serve as emperor. This also gave Sejanus an uncle, Junius Blaesus, who would serve as proconsul in Africa in 21 CE and later receive triumphal honors.
When Sejanus himself married Apicata, sister of the exceedingly wealthy Marcus Gaius Apicus, with whom he had three children, he probably had every expectation of a successful political career in Rome.
Prefect of the Praetorians
When Julius Caesar was made dictator for life in 44 BCE, it was clear that his power was based on the military force that he could personally command, rather than consensus from Rome’s senatorial elite. He was assassinated for this, but the balance of power in Rome had already moved from political allegiances to military might.
Caesar’s successors Marcus Antonius and Octavian Caesar divided the Roman Empire between themselves based on their military forces. When Octavian emerged as the sole victor following the Battle of Actium in 31 BCE, the loyal troops behind him were the backbone of his power. He had to find a way to justify having some of his military in Rome when he no longer had a rival.
One of the many things Augustus did to secure his military position was create the Praetorian Guard in 27 BCE, the same year he adopted the name Augustus. The guard was a group of nine cohorts, one less than the ten needed to make it a Roman legion, which meant that he could claim that it was a guard rather than an army. They were principally responsible for protecting Augustus and the members of his family, on which the prosperity of Rome now depended. Augustus also exploited them as a city security force and a highly organized administrative team.
The role of leader of the Praetorian Guard, known as a prefect, was therefore a powerful one. Following the example of Rome’s consuls, Augustus appointed two prefects, so that no single man would have too much power. They were also appointed from the less politically threatening class of equites.
Sejanus’s father, Lucius Seius Strabo, was made one of those prefects under Augustus. After the death of the emperor in 14 CE, his successor Tiberius appointed Sejanus as prefect alongside his father. Not long after, probably the following year, Strabo left Rome to become governor of the strategically important province of Egypt, Rome’s breadbasket. For reasons unknown, Tiberius seems not to have appointed another Praetorian Prefect at the time but left Sejanus in sole command.
Socius Laborum
Sejanus seems to have been ambitious from the very beginning and wasted no time building his power base. Not long after becoming sole prefect, he increased the number of cohorts in the Praetorian Guard from nine to twelve and moved them from small garrisons spread throughout the city to a single garrison. He also ensured the loyalty of his troops by appointing each military tribune and centurion personally. This gave him command over an army of 12,000 loyal soldiers in Rome.
At least initially, Sejanus seems to have acted with the full support of the new emperor Tiberius, who exhibited the guard in parades to show his power. The emperor seems to have been pleased with Sejanus, calling him his Socius Labroum, “partner in all my labors,” allowing a statue of Sejanus to be erected in the Theater of Pompey and granting requests to appoint Sejanus’s allies to public offices in Rome and the provinces.
In 15 CE, when the military legions in Germania and Pannonia revolted, Tiberius dispatched Germanicus to deal with the troops in Germania. He sent his own son Drusus to Pannonia with the support of Sejanus and two Praetorian cohorts.
It is also clear that at this time Tiberius saw Sejanus as a trusted aid, but he looked to his Julio-Claudian family for his successor. While Germanicus was Tiberius’s presumed heir, he also gave his son Drusus opportunities to make a name for himself as a general, as Tiberius had done under Augustus. As an example, Drusus commanded troops in Illyricum in 18 CE.
When Germanicus died unexpectedly the following year, even more attention was given to Drusus. He served as consul with Tiberius in 21 CE, and in the following year, he shared his Tribunician power with Drusus, clearly indicating him as his successor.
Gathering Influence
Despite not being a member of the Julio-Claudian family, Sejanus seems to have coveted the power that Tiberius was granting to Drusus. In 20 CE, Sejanus tried to have his daughter Junilla engaged to the son of Claudius, who at this time would have been one of the more accessible members of the Julio-Claudian family due to his distance from power. It was clearly a strategic move, as the girl was only four years old. It never happened because the boy died a few years later.
Nevertheless, Drusus seems to have been keenly aware of Sejanus’s ambition. According to Tacitus, in 23 CE Drusus struck Sejanus following an argument, lamenting that Sejanus was asked to assist an emperor who had a living adult son.
Sejanus was very aware of the threat that Drusus posed to his position. He could not expect to continue to be prefect if Tiberius died and Drusus was to succeed him. This is probably why Sejanus began a relationship with Livilla, Drusus’s wife. According to confessions made many years later, Sejanus and Livilla slowly poisoned Drusus, eventually leading to his death in 23 CE. Sejanus then tried to marry Livilla, but his request was denied by Tiberius.
The sources suggest that Tiberius scolded Sejanus for overstepping his rank. It is also likely that Tiberius’s mother Livia, and Livilla’s mother Antonia, objected to the match.
While Sejanus’s plan may simply have been to remove Drusus as a threat, he had a much greater impact. The death of his son contributed to Tiberius’s disillusionment with power and life in Rome. In 26 CE, with the encouragement of Sejanus, Tiberius retreated to the island of Capri and began ruling in absentia. With the Praetorians responsible for his protection, Sejanus was in full control of access to the emperor, who also delegated broad powers to Sejanus in Rome.
Regent in Rome
Over the next few years, Sejanus was regent in Rome, operating on behalf of Tiberius but with significant independent power to do as he pleased. Initially, his ambition seems to have been kept in check, probably by Tiberius’s mother Livia, who was extremely influential as the widow of Augustus, and by Agrippina, the wife of Germanicus.
Following her husband’s death, Agrippina came to Rome and made no secret of blaming Tiberius for what happened to Germanicus. Also, following the death of Drusus, she was open in her ambition that one of her three sons, Nero, Drusus, or Gaius (Caligula) would succeed Tiberius. This seems to have displeased Livia, and the animosity between the two may have prevented them from uniting against Sejanus.
Livia died in 29 CE, giving Sejanus more power. In 30 CE, he accused Agrippina of conspiring against Tiberius and had Agrippina and her two older sons exiled, where they would eventually die. Her youngest son Gaius would be sent to Capri to live with his uncle. There he would indeed be groomed for power, just as Agrippina had wished.
It was not just the family who suffered, Sejanus used accusations of treason to cull the capital of senators and wealthy equites. He eliminated those who opposed him and filled the imperial coffers, which were now Sejanus’s coffers.
In 31 CE, Sejanus made himself consul alongside Tiberius in absentia, and he finally secured his engagement to Livilla, meaning that he would soon be a Julio-Claudian. At the start of the year, it looked like Sejanus might indeed be able to succeed Tiberius as the next emperor, or at least as regent for one of Tiberius’s young relatives, his nephew Gaius or grandson Tiberius Gemellus.
Downfall of Sejanus
Unfortunately, we don’t really know how the tide turned against Sejanus since the text from Tacitus, our most reliable historical source on the matter, is lost. But it seems that Tiberius became aware that Sejanus’s ambition was greater than he had thought. The emperor decided to remove him.
According to Cassius Dio, writing centuries after the fact, Tiberius was concerned that Sejanus was too powerful to remove directly, so he started sharing misinformation. Tiberius sent letters to Rome praising Sejanus to some and vilifying him to others. He would also claim that he was due to arrive in Rome in a matter of days or was on death’s door. This seems to have let Tiberius measure support for Sejanus in the capital and determine the best way to move against him.
Tiberius needed a new commander of the Praetorians, and he enlisted Naevius Sutorius Macro, the prefect of the vigiles, the city’s fire brigade. He gave him a letter telling him exactly how and when to take control of the Praetorians.
He also sent a letter to Sejanus, sending him to the senate house on October 18th, 31 CE to receive tribunal powers, which would ostensibly mark Sejanus as his heir. When Sejanus arrived, a letter was read in the senate asking them to grant Sejanus this new honor. But it was also at this time that Naevius was to take control of the guard and surround the senate house with his vigiles. The same letter then denounced Sejanus and told the senate to take him into custody. Despite much confusion, this was done successfully.
That same evening, the senate met in the Temple of Concordia and reviewed the charges of treason against Sejanus. He was convicted and killed. His body was thrown from the Gemonian Stairs, a traditional location for executions in Rome. Probably trying to win favor with Tiberius, the senate took things further and ordered damnatio memoriae, which meant that all Sejanus’s statues were torn down, and his name was erased from inscriptions, historical records, and even from coins.
Many of Sejanus’s supporters were also rounded up and killed, including all his children. Apparently, his daughter Junilla was raped before she was killed, as it was considered unspeakable to execute a virgin for treason. This is when Livilla was questioned and admitted to poisoning Drusus before killing herself. Her servants confirmed the accusation under torture, though this is a notoriously unreliable way to get true information.
Many of Sejanus’s supporters were tried for treason and killed, and the senators whose family and friends were previously prosecuted by Sejanus rejoiced. But their joy was short-lived.
The Impact of Sejanus on Tiberius
Tiberius was already seriously disillusioned with imperial power before he went to Capri following the deaths of Germanicus and Drusus. The betrayal he felt from Agrippina and her elder children probably didn’t help. To now have been betrayed by Sejanus, the one man whom he seems to have trusted over the years, seems to have broken Tiberius.
The emperor, still hiding away in Capri, trusted no one. The treason trials initiated under Sejanus continued but with a focus on Sejanus’s allies. In reality, with informants exploiting the opportunity to enrich themselves and deal with past enmities, no one was safe.
Tiberius also gave up on securing his succession. He did not give Gaius Caligula any special powers or titles or the opportunity to build a military reputation. Tiberius’s grandson Tiberius Gemellus was only a teenager and all but ignored. Nevertheless, when Tiberius died in 37 CE, Caligula became the new emperor. This was described as a moment of rejoicing because Tiberius was so feared and hated at the time of his death.
These sad years at the end of Tiberius’s reign overshadowed any good Tiberius may have done and he became a villain for Roman historians. This turning point in his reign can largely be traced to the ambition and betrayal of Sejanus. Nevertheless, it would be Caligula who would suffer a damnatio memoriae after his death, in the same way as Sejanus.
