After the Social War, the socii were all granted Roman citizenship, the Latin alae abolished, and the socii recruited into the legions.By the outbreak of the Second Punic War, the Romans were remedying the legions' other deficiencies by using non-Italian specialised troops.Until 200 BC, the bulk of a Roman army's cavalry was provided by Rome's regular Italian allies (socii), commonly known as the "Latin" allies, which made up the Roman military confederation.This was Rome's defence system until the Social War of 91–88 BC.From then, Roman armies were always accompanied by large numbers of non-Italian cavalry: Numidian light cavalry and, later, Gallic heavy cavalry.For example, Caesar relied heavily on Gallic and German cavalry for his Conquest of Gaul (58–51 BC).Panel from Trajan's Column, Rome The Auxilia (Latin, lit."auxiliaries") constituted the standing non-citizen corps of the Imperial Roman army during the Principate era (30 BC–284 AD), alongside the citizen legions.
The auxilia thus represented three-fifths of Rome's regular land forces at that time.
Like their legionary counterparts, auxiliary recruits were mostly volunteers, not conscripts.
The Auxilia were mainly recruited from the peregrini, free provincial subjects who did not hold Roman citizenship and constituted the vast majority of the population in the 1st and 2nd centuries (c. In contrast to the legions, which only admitted Roman citizens, members of the Auxilia could be recruited from territories outside of Roman control.
By the end of the period, there were no significant differences between legionaries and auxiliaries in terms of training, and thus, combat capability.
Auxiliary regiments were often stationed in provinces other than that in which they were originally raised, for reasons of security and to foster the process of Romanisation in the provinces.
Despite its formidable strength, the legion had a number of deficiencies, especially a lack of cavalry.