Auxiliary soldiers and the Roman army
Serving alongside the heavy infantry of the Roman legions were regiments of auxilia, mostly about 500 strong, who provided light infantry and cavalry together with specialist troops like archers and slingers. Their mobility made them ideal as scouts and flank-guards on campaign, and they were also used for routine patrolling and defence. Increasingly they joined the legions in the forefront of battle.
The auxiliaries were normally recruited from new provinces of Rome or tribes outside the Empire, and their equipment and dress sometimes reflected their origins. Usually, however, in the first to third centuries AD, they wore an iron mail shirt or bronze scale tunic and carried a flat shield of oval, rectangular or hexagonal shape. Their swords tended to be longer than the legionary gladius (short sword), whilst spears differed from unit to unit.
Unlike the legionaries, the auxiliary forces were not usually Roman citizens. They were, however, granted citizenship after twenty-five years of service. Evidence for this is seen in the discharge diplomas: engraved bronze plaques which recorded the service of the individual soldiers. When Roman citizenship was granted to all free-born inhabitants of the Empire in AD 212, the distinction between the legionary and auxiliary forces declined and disappeared.