What was the role of the Praetorian Guard in Roman History?

Praetorian Guards from the 1st century AD

The Praetorian Guard was critical in the politics and government of Imperial Rome for approximately 300 years. This military unit was unique and wielded power and influence in Rome. They were the guardians of the Emperors and sometimes their masters. This article will examine the role of the Guards in Roman history. It will demonstrate that they had the power to remove weak Emperors and became important power brokers in the Empire.

For most of their history, they were the loyal protectors of the leader of the Roman World. The Guards were also an important military unit who played a significant role in maintaining peace and security in Rome and throughout Italy. The guards also played a meaningful role in the administration and policing of the capital of the Empire and Italy.

The Praetorian Guard Composition

The Praetorian Guards were an elite unit in the Imperial Army, and their role was to protect the person of the Emperor, a task they shared with the Imperial German bodyguard.[1] They were the only army unit allowed to bear arms in Rome, but out of respect to Republican sensibilities, they never wore armor in the city’s precincts. The Guards were divided into some cohorts, that numbered several hundred men typically. The various cohorts were composed of infantry and cavalry. For the first few centuries, they were mainly recruited from central Italy, and many were able to secure admission because of family or political connections.[2]

Over time more and more experienced legionnaires joined the Guards. The Praetorians were organized under a Praetorian Prefect, who became a vital military and political figure. The Prefect was eventually to command not only the guard but the urban militia of Rome. The individual cohorts were under the command of a tribune. Those who served in the Guards had better pay, conditions and a shorter service than regular legionnaires. They were usually members of the Equestrian Order, which meant that they were from a high social class until at least 195 A.D when Septimius Severus reformed the Guard.[3] The Guards were seen as a great way to advance the career of the ambitious and its members had a great deal of social prestige.

The History of the Praetorian Guard

The Battle of the Milvian Bridge

During the decline of the Roman Republic, the various generals who competed for power and influence often created their bodyguard. The name Praetorian- comes from the Latin, for General’s tent. Julius Caesar was one of the first to use a unit of handpicked soldiers for his protection. His heir, Octavian (later Augustus) and his bitter rival Mark Anthony both had personal bodyguards. When Augustus became the sole ruler of Rome and its Empire, he created three cohorts of guards, that became known as the Praetorian Guard. One was stationed in Rome to protect the Emperor, along with his German bodyguard and two were located throughout Italy to maintain order.

Initially the guards were tightly controlled by the first Emperor, however under his heir Tiberius, the Praetorians became very influential. Under the command of the ambitious and scheming Sejanus, they were all concentrated in Rome, and he built a base for them in the city.[4] This meant that the Praetorians were the dominant power in Rome and this continued after the fall of Sejanus after his plot to become Emperor failed. Under the insane and bloody Caligula, they became very influential in Rome. Indeed, one of the tribunes of the Guard assassinated Caligula after being insulted by the mad-Emperor. The guards after the assassination of the Emperor selected Claudius as the supreme leader of the Roman World, and he handsomely rewarded the Praetorians.[5]

By this stage, the Guards had become a real power in Rome, and Claudius even issued coins bearing the symbol of the Imperial Bodyguard, indicating their influence at this time. The Guards later conspired against Nero, who upon hearing that he had lost their support decided to commit suicide, believing that all was lost. During the Year of the Four Emperors (69 AD), they installed and deposed Galba as Emperor and sold the Imperial diadem to Otho.[6] Vitellius upon seizing Rome curbed the power of the Imperial Bodyguard. However, when Emperor Domitian (97 AD) began to act brutally and unpredictably, he was assassinated, and the Imperial bodyguard was implicated in his death.[7]

For a century the Praetorian Guard were controlled by a series of strong rulers, especially during the reigns of the ‘five good emperors.’[8] However, Emperor Caracalla indulged the Praetorian Guard, and they recovered much of their power. When he was assassinated in a Palace conspiracy, the Praetorians took over and brutalized the city. In 193, the Guard auctioned of the Imperial office after killing Pertinax, who attempted to curb their power and limit their privileges.[9] Septimius Severus, after he became Emperor, reformed the Praetorians and he ended the traditional Italian and Equestrian domination of the Imperial guard.

By 230 AD the Empire fell into an existential crisis, this is the period known as the ‘Third Century Crisis.’[10] This was a period when a series of solder-emperors fought for the Empire, and the Roman World fell into anarchy and economic decline. During this time a Praetorian Prefect, Macrinus, a Thracian giant, became Emperor for a year, before being killed.[11] A series of energetic generals ended the anarchy, and from Diocletian onwards, Rome was no longer the center of the Roman World. He used his soldiers as his bodyguards, and the Praetorians were side-lined. In 303 A.D, when Constantine invaded Italy, the Praetorians backed his rival. At the Battle of Milvian Bridge, the Guards were almost annihilated. The surviving guardsmen were sent to the frontiers of the Imperial territory, and their barracks was demolished on the orders of Constantine.

The Praetorian Guards- power-brokers

A Praetorian soldier from the 2nd century AD

The Praetorian Guards were usually the only significant military unit in Rome if not Italy. There was an urban militia (vigiles), and the German bodyguard of the Emperor, however, the Guards were by far the most formidable military force in the capital. This and their unique access to the Emperor meant that they were in a position to intervene in Imperial affairs. The Emperor came to depend on the Guard for his safety, and over time the Imperial bodyguard began to become ‘conscious of their power.’[12] The ruler of the Roman World was at their mercy if they acted in unison and decisively. They Guards were instrumental in the deposition of countless Emperors the exact number is unknown.

The Praetorians because of their proximity to the absolute ruler of the known world knew that his power depended on deference and the unthinking obedience of the population. The Imperial Bodyguard, under Prefects such as Sejanus, recognized that ultimately power depended on brute force and that they had a monopoly on violence in Rome. As a result, the Imperial Guard played a considerable role in the history of the Empire. They had the ability, which the Senate did not have of making and unmaking the absolute ruler of the Roman world. The guards only deposed Emperors who were weak or during times of crisis. For the majority of their existence, strong rulers controlled the elite bodyguard. There are long periods in the 2nd century, for example, when the bodyguard is not mentioned in the sources, because they were tightly controlled by rulers, such as Hadrian.[13]

Military role of the Praetorian Guards

The Imperial guard was a formation of the army, and Emperors often deployed them in the field. The Praetorian cohorts often accompanied Emperors on the campaign, where they protected their sovereign. For example, they accompanied Trajan on his campaign in Dacia, and this is memorialized on the Arch of Trajan in Rome. It was not uncommon for the Imperial Bodyguard to take part in the battle and they were regarded as an elite unit, who was often used when the outcome of a battle was uncertain. On one occasion they accompanied Germanicus as he quelled a great mutiny among the legions on the Rhine, who were threatening the new Emperor Tiberius. They helped Germanicus to persuade the legionnaires to return to their camps and restore discipline.[14] For many Emperors, they were seen as the last line of defense against a mutinous army or the legions of a rival.

Security and other roles in Rome

The Praetorians as the main military force in Rome were required to carry out a wide range of duties. Despite the sophistication of the Roman state, it had no police force or many of the other organizations that modern society takes for granted. The Imperial Body Guard played a crucial role in the policing of Rome. The city was a vast and diverse metropolis, and much of it was lawless and ruled by gangs. The Praetorian Guards were often the only force that was able to police the city. They did this was a great effect, and they helped to ensure stability in the sprawling city on the Tiber. Marcus Aurelius, for example, used cohorts of the Guards to police the city, during his many long absences on campaigns against Germanic tribes. They also appear to have been used for crowd control during the Games. Many Emperors appeared to have used the Imperial Bodyguard as a secret police force. There are accounts of guardsmen being employed to spy on real and imagined conspirators, and they appear to have been used to intimidate those who threatened the position of an Emperor.

The Praetorians appear to have been used not only to guard the Emperor but also maintained their authority in the capital.[15] There are claims that the guards would often secretly assassinate those who were believed to be a threat to the Emperor. It seems that the Imperial Guardsmen were flexible and used in emergencies. The elite unit was often used as firefighters, alongside the urban militia. For example, Praetorian Guards fought a fire that threatened the Temple of Vesta in the great conflagration that engulfed the city on the Tiber, during the reign of Nero. [16]

Praetorian Guards in the Provinces

While the Imperial Bodyguard was mainly stationed in Rome, it was not uncommon for Praetorian officers to be located elsewhere in Italy. The Praetorian Prefect was important in the government of Italy. There is evidence that Praetorians could be stationed throughout Italy. Imperial Bodyguards often administered areas and urban centers in Italy. For example, the graves of Praetorians have been found in Pompeii, where they were presumably involved in local affairs. It was believed that Praetorians had a role in collecting taxes and maintaining law and order. They would, presumably, ensure that the orders of the Emperor were enforced at the local level. It is believed that Praetorians were employed to arbitrate in local land disputes between communities, which often threatened to flare up into open violence.[17] It also appears that they were involved in the collection of taxes. The exact role of the Praetorian in the Italian provinces is unknown, but it appears that they played an important role in the administration of Italy.


The Praetorian Guards were an important institution in the history of Imperial Rome. They were used to guard the Emperor and to protect his person and his family. This was a critical task in any autocracy such as the Roman Empire. However, they were in a privileged position to determine if an emperor should stay in power. Praetorian Guards never ousted a strong Emperor, but the Imperial bodyguard was often a destabilizing factor in Imperial politics.

Additionally, they helped to precipitate periods of war and political violence, such as the Year of the Five Emperors (195 AD). However, they were not only power-brokers. Still, they also played a critical role in the administration of Rome and the Italian provinces. The Praetorian Guard alternated, in its three hundred years from being a group that helped to stabilize the Empire to a body that destabilized Rome.

Further Reading

B. Rankov. The Praetorian Guard (London, Penguin, 1994).

de la Bédoyère, Guy (2017). Praetorian: The Rise and Fall of Rome's Imperial Bodyguard. (Yale University Press, 2017)

Echols, Edward. "The Roman City Police: Origin and Development." The Classical Journal 53, no. 8 (1958): 377-85

Smith, R. E. "The Army Reforms of Septimius Severus." Historia: Zeitschrift Für Alte Geschichte 21, no. 3 (1972): 481-500

Collins, A.W. "Casperius Aelianus, Trajan and the Mutiny of 97 AD." Acta Classica 56 (2013): 55-61.


  1. Bingham, Sandra. The Praetorian Guard: A History of Rome's Elite Special Forces (London, IB Tauris, 2013), p 118
  2. Bingham, p 119
  3. Bingham, p 201
  4. Tacitus, The Annals of Imperial Rome, x, iv
  5. Tacitus, xi, v
  6. Suetonius. Life of Otho, vi
  7. Suetonius, Life of Domitian, vi
  8. Bingham, p. 234
  9. Bingham, p 213
  10. Bingham, p. 278
  11. Gibbon, Edward, The Decline and Fall of the Roman Empire (London, Penguin Books, 1985), p 245
  12. Bingham, p. 167
  13. Bingham, p 178
  14. Tacitus, x, v
  15. Bingham, p 117
  16. Tacitus, xi x
  17. Kelpie, p 116

Updated December 18, 2018.