The Praetorian Guard: the emperors’ fatal servants

The over-mighty, over-paid and over-confident armour-plated racketeers were angry.

At the end of AD 192 the profligate emperor Commodus had been murdered. He was followed by Pertinax, a stickler for discipline. Pertinax’s attempts to reform the Roman world came up against the Praetorian Guard.

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The guard was supposed to be made up of hand-picked men. By the end of Commmodus’s reign it was hard to know why they were appointed at all – unless the qualifications were indolence, greed, and cynicism.

So indulged had the Praetorians been by Commodus, they decided on a simple solution. They killed Pertinax after 87 days.

The climax came when Didius Julianus unwisely offered the soldiers 25,000 sesterces a head, a vast sum. That clinched it. The Praetorians made him emperor but overlooked the precaution of asking to see the money first.

Unable to pay the money, which he didn’t have, the foolhardy Didius was toppled after just 66 days. Meanwhile a senator and general called Septimius Severus was busy seizing power the time-honoured Roman way: with force. His victory was followed by a cashiering of the Praetorian Guard and its total reformation with new men.

Supreme power

It is easy for us to imagine the Roman empire as a place ruled by order and systems, checks and balances. In reality it was a collection of cobbled-together compromises.

There wasn’t technically even a position of ‘emperor’. The word imperator means general, and it was one of a collection of Republican offices that were vested in one man who in practice, but not theory, had supreme power.

The first man to hold that supreme power was Augustus. He came up with the ingenious idea of being granted the powers of the office (rather than the post itself). Thus he could pose as a defender of the people within the framework of the old Republic.

It was nonsense of course and everyone knew it. The Augustan system was a brilliant solution to the chaos of the civil wars of the late Republic. Tacitus said everyone went along with it because of “the enjoyable gift of peace”. But it placed power on a knife edge, for the whole edifice was built on the prestige of one man. Augustus had relied on the naked use of military force. Once in power, he did all he could to cloak that force in legitimacy. So, the army was reduced in size.

Augustus created potentially the most dangerous institution the Roman world had ever seen

Military power, however, remained key. During the civil wars, most of the generals made sure they had a Praetorian bodyguard, made up of selected men. As the last man standing, Augustus hung on to his and formalised it into the permanent Praetorian cohorts.

Praetorians enjoyed better pay and conditions than legionaries, and served for far less time. They existed to protect Augustus, but he dispersed two-thirds of them round Italy to minimise the impression that he depended on them. Instead, the guard depended on Augustus. No emperor meant no jobs and no special status.

But this state of affairs was reliant upon the emperor having enough prestige and power to contain the guard. Augustus had created potentially the most dangerous institution the Roman world had ever seen.

In his monumental The Decline and Fall of the Roman Empire, Edward Gibbon described this brilliantly: “By thus introducing the Praetorian Guards, as it were, into the palace and the senate, the emperors taught them to perceive their own strength, and the weakness of the civil government; to view the vices of their masters with familiar contempt, and to lay aside that reverential awe, which distance only, and mystery, can preserve towards an imaginary power. In the luxurious idleness of an opulent city, their pride was nourished by the sense of their irresistible weight; nor was it possible to conceal from them, that the person of the sovereign, the authority of the senate, the public treasure, and the seat of empire, were all in their hands.”

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Small but lethal

So the seeds of the events of AD 193 had been sown by Augustus more than two centuries earlier. It took a while for the Praetorians to realise how much power they had. There were not that many of them, though establishing exactly how many is remarkably challenging. All we know for certain is that by the early third century there were 10 cohorts with 1,000 men in each, roughly equivalent to two legions. Based on an earlier reference by Tacitus, there may have been only nine cohorts of 500 men each in Augustus’s time.

Does it matter? Not really. What does matter is that the guard’s influence dramatically outweighed its size. Crucially, that power was only wielded when the emperors failed to live up to the guard’s expectations. Sadly, over the three centuries of its existence, those expectations substantially increased.

The first big change since the guard’s creation was the idea of Sejanus, prefect of the Praetorian Guard under Tiberius (ruled AD 14–37). Spotting the potential the command of the Praetorians offered him, this ruthless opportunist brought the whole guard into Rome, ordering the construction of the Castra Praetoria.

The Praetorian Guard’s influence dramatically outweighed its size…

From here Sejanus wormed his way into Tiberius’s trust, planning to marry the emperor’s daughter-in-law and establish himself as the emperor’s successor. Tiberius raised him to a “high pinnacle of glory” and, wrote Cassius Dio, even called him “my Sejanus” and “my partner in labours”.

Fortunately for Tiberius the penny dropped in time. Sejanus’s fall in AD 31 was dramatic and brutal. He and his family were killed, and “the populace slew anyone” who had associated with him. But the guard stayed in Rome. When officers of the guard murdered Tiberius’s successor, Caligula, in AD 41, the Praetorians were on hand to change the course of history. “Take that!” yelled Cassius Chaerea, the first to strike a blow. With the volatile young emperor dead, there were plans afoot to restore the Republic. That would end the privileged jobs the Praetorians held.

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Curtains for Claudius?

In one of the most celebrated events in Roman imperial history, the guardsmen came across Caligula’s uncle Claudius, the last remaining eligible male member of the Julio-Claudian family. The historian Suetonius tells us that he had “hidden among the curtains” in the imperial palace. Dismissed by his family as an idiot, history had passed him by – until now.

Claudius was declared emperor by the Praetorians and no one, including the senate, was in any position to argue. The Praetorians’ jobs were secure. Claudius was a reluctant emperor and turned out to be a good deal more competent than his family thought him capable of. It’s even possible that Claudius had been in on the plans all along. Gold and silver coins were issued showing the guard welcoming the new emperor, and he them.

The coins almost certainly formed part of the donative Claudius paid the Praetorians on his accession. Those payouts added to the higher rates of pay and the bequests in each emperor’s will. Not surprisingly the amounts generally increased – and that is why the ghastly events of AD 193 took place.

The remarkable thing is that the auction of 193 did not happen earlier. During the first century AD, after Claudius’s accession, the Praetorians played a frequent part in the imperial story – especially under Nero.

Nero’s Praetorian prefect, Tigellinus, who, wrote Cassius Dio, “outstripped all his contemporaries in licentiousness and bloodthirstiness”, devoted his time to facilitating his master’s tastes for decadence and perversion. Meanwhile the guardsmen became extras in Nero’s public performances.

But from AD 96 until the accession of Commodus in 180 we hear almost nothing about the guards. That crucial balance, identified by Gibbon, had swung towards the emperors. The men who controlled the Roman world between AD 96 and 180 – among them Trajan, Hadrian, Antoninus Pius and Marcus Aurelius – were highly capable rulers who were regarded with sufficient esteem to escape being challenged by the guard. The Praetorians were held in check. They were arrogant, elitist and smug but contained.

In a world where the state had almost no other means of asserting its authority, the army was used for far more than fighting and posturing. Praetorians were sent to guard grain routes in Numidia, specialised in trades such as lead working, dispatched to resolve boundary disputes in civilian communities, and even under Nero were sent to explore the upper reaches of the Nile.

Prostitutes and parties

But the death of Marcus Aurelius in AD 180 marked a turning point. The accession of his weak-minded son Commodus created a power vacuum into which the Praetorians themselves were sucked.

More interested in prostitutes, parties and performing in the arena, Commodus was easily persuaded to leave affairs of state to his opportunistic and self-serving Praetorian prefects. The soldiers themselves degenerated into louche layabouts, unrecognisable as a meaningful military force.

Septimius Severus’s new guard turned out to be no better than the old one. The fallout from Praetorian ambitions, soldiers and prefects alike, scattered across the third century like a hailstorm.

Emperors rose and fell like ninepins, some of them murderously ambitious Praetorian prefects who seized power but were later killed by their own men. In the end the guard backed the wrong man and was permanently disbanded in 312 by Constantine, determined to destroy one of the major causes of the chronic instability of the era.

Menacing, mercurial and mercenary, the Praetorians were only kept under control by emperors who had enough personal prestige to command their loyalty. So the guard serves as a warning to any leader today whose power is sought, won and sustained through force, however skilfully cloaked in the paraphernalia of legitimacy and popular consent.

Augustus understood that. Not all his successors did. The guard emerged as the most dangerous imperial possession, making and breaking emperors until their final gamble cost them their very existence.

Guy de la Bédoyère is a historian and broadcaster, specialising in ancient Rome. His books include The Real Lives of Roman Britain (Yale, 2016).

This article was first published in the March 2017 issue of BBC History Magazine.