The role of allied legions would eventually be taken up by contingents of allied/auxiliary troops, called "Auxilia". Each legion had a same size or near same size Auxilia (auxiliary), which contained specialist units, engineers and pioneers, artillerymen and siege craftsmen, service and support units plus units made up of non-citizens (who were granted Roman citizenship upon discharge) and undesirables. These were usually formed into complete units such as light cavalry, light infantry or "velites", and laborers. There was also a reconnaissance squad of 10 or more light, mounted infantry called "speculatores" who could also serve as messengers or even as an early form of military intelligence service.