The Praetorian Guard was recruited initially by Augustus Caesar. While the later imperators, such as Caesar, Anthony and Octavian certainly had their own personal guardsmen, it wasn't until Octavian became Augustus, that the Praetorian Guard was established as an institution. At the onset, Augustus recruited 9 cohorts of about 500 men each, almost equal to the size of an imperial legion. These cohorts were lead by "The Perfects" who wielded great political and military power. The Perfects eventually became a formidable political force, and in many cases, both eliminating the current Emperor and placing a replacement to the throne.
The Praetorians were originally recruited from the best available veteran Roman Legionaries. Contrary to popular belief, the Praetorians, especially beyond the Julio-Claudia era, often went on campaign with the Emperor. Enemy incursions into Italy or nearby provinces were also often met by Praetorian defenders. Praetorians received sesquiplex stipendum, or pay and a half to that of the legions.
Service for 16 years to the emperor could make a soldier considerably wealthy.
"After the death of Augustus, under whose reign the Praetorians were unquestionably loyal, the political advancement of the guard began in earnest." During the reign of Tiberius, the Perfect Lucius Sejanus became an infamous tyrant, using his power to openly assassinate political opponents. Eventually he was killed. It was during this period that the Castro Praetorian was built, and most of the Praetorians were moved to Rome. Tiberius's heir was murdered by the Praetorians because of his insolence. Claudius, his uncle was the first emperor to essentially be forced into power through the political machinations of the Praetorians. The Guard willingly altered loyalty between whichever man took power, and became so powerful that they elevated and deposed of emperors according to their pleasure. Emperor Vitellius increased the Guard to...