One way to attain (or regain) citizenship in the Terran Empire is to serve a 5-year tour of duty with the Imperial Legionnaires. While mainly used to garrison Imperial planets, they also accompany mechanized troops during offensive campaigns.
Legionnaires are equipped with Terran-manufactured G-Lock 8 Photon Rifles (based on the older Welby-Simms MK-7 design) and High-Density Combat Armor. Their main role is to take out enemy infantry, but can also be put to good use when fortifying buildings or manning gun emplacements. They are generally weak on the battlefield when deployed in small numbers.
Legionnaire squads are usually comprised of ex-convicts, troublemakers and other lower-class individuals, which make them largely expendable in the eyes of Imperial Centurions and other battlefield commanders.