A classic work of military history, this is the first systematic study of the auxiliary soldiers who accompanied the ancient Roman legions into battle. Using evidence ranging from their gravestones to the discharge papers that eventually granted them citizenship, Cheesman traces the evolution of the “barbarian” auxiliaries, from ad-hoc local levies to highly specialized units that became a vital component of the Roman army. Separate chapters cover the size and organization of auxiliary units; where and why auxiliaries and their officers were recruited; their role in war and frontier defense; and the different kinds of arms and armor they used. A final conclusion deals with the decline and break-up of the Augustan military system, and the fates of auxiliary units left to defend forts far from their homelands. Two appendices list the strength, positioning, and recruitment areas of all known auxiliary units in the peak years of the second century AD.