For four centuries, from the civil wars of the Late Republic to Constantine's bloody reunification of the Empire, elite corps of guardsmen were at the heart of every Roman army. Whether as bodyguards or as shock troops in battle, the fighting skills of praetorians, speculatores, singulares and protectores determined the course of Roman history.

This title details the changing nature of these units, their organization and operational successes, and failures from their origins in the late Republic through to their unsuccessful struggle against Constantine the Great.