The Praetorian Guard was a special guard for the Roman Emperors. Before the name was used for the emperor's guards, the title was used for the guards of the ascending generals of the Scipio family. Constantine I abolished the guards in the 4th century.
The term “Praetorian” is derived from the tent of the general (or praetor) of a Roman army unit on the battlefield — the praetorium. It was customary for the rulers to choose soldiers to guard their tent, and to join the owner of the tent. They consisted of infantry and cavalry. At this time, Cohorts (military unit) cohorts were still recognized as cohors praetoria, and several prominent rulers had a group of them, including Julius Caesar, Mark Antony, and Augustus (Octavian). Julius Caesar, thanks to Legio X Equestris, found that a unit even better than his fellow legions was a great help during the war. When Augustus became emperor, he saw the unit as a tool not only for war, but also for non-participation in politics. So, from the legions of the provinces, he recruited praetorian guards.
Original look of the Guard
The original guard was very different from the later guard groups, who in turn would protect the emperor, thus instead threatening its power. Augustus understood the need for someone to protect him in Rome, but he was careful not to violate the power of such protectors. Thus, he formed only nine cohorts, each with 1000 (500 initially) soldiers. Only three of these groups existed in Rome. There was also a small group of detached cavalry units (turma) each with 30 men. While the Guard patrolled the large edifice and the palace, others were stationed in towns near Rome. In 2 BC, two Praetorian Prefects were filled. In that system, and in Augustus’s kitten eye, no internal threat arose from the Guard.
The death of Augustus on August 19, 14, marked the end of the peace of the Praetorians. Throughout the history of the Guard, Augustus was really the only one they served with complete allegiance. In subsequent reigns, they exaggerated their personal ambition and participated in politics.
The ambitious Lucius Aelius Sejanus, who became a prefect in Tiberius' time, was one of the first to use the guard for their personal interest. He moved the guards from Italian towns to the city of Rome, and forced the emperor to build Castra Praetoria (Praetorian camp) right outside Rome. As a result, Sejanus summoned all the guards of Rome itself. And again, the whole guard was already at the emperor’s will, but the emperor was also already at the mercy of the guards. A great example of this is the incident in 31 AD, in which Tiberius relied solely on his cohors praetoria against Sejanus' mialsang guards. Although Tiberius defeated Sejanus in the ensuing battle there, the praetorians showed their potential political power.
After Sejanus ’death, the guards began to get involved in the political game. With money, or perhaps of their own free will, they assassinated some emperors, they oppressed their own prefect, and threatened the Roman Senate. At 41, they assassinated Caligula and succeeded Caludius to the throne, with them challenging the senate to oppose their actions.
The year 69 was one of the bloodiest years the guard entered, the Year of the four Emperors. After emperor Galba failed to give a donativum (imperial gift) to the guard, they crossed over to Otho and killed the emperor.