The document discusses the history and evolution of the Praetorian Guard in ancient Rome. It began as the private militia guarding Roman generals but was established as a permanent bodyguard for emperors by Augustus consisting of 9 cohorts totaling over 4,500 men. Over time, the Praetorian Guard gained political influence and the ability to influence imperial succession and commit crimes without punishment. By the 2nd century AD, they had become a threat to the stability of the empire and were eventually replaced under Constantine.