In the long, turbulent history of the Roman Empire, no military unit cast a longer shadow over the fate of emperors than the Praetorian Guard. For over four centuries, these elite soldiers served as the personal bodyguard of Rome's most powerful men and, when it suited them, as their executioners. They were the best-paid, best-equipped soldiers in the Roman world, stationed at the very heart of imperial power. Their story is one of loyalty and betrayal, of discipline and corruption, and of the dangerous entanglement between military force and political authority that would come to define the later Empire.