Many Roman soldiers were 'auxiliaries'. This name means 'helpers'. They were not regular Roman soldiers. They came from non-Roman tribes and wore very different uniforms. They were formed into special cohorts (infantry units) or alae (cavalry units). Many of them were stationed at the forts on Hadrian's Wall. Each cohort was from a different part of the Empire and had a special ability like: skilled horse-riding archery rock slinging spear throwing some other special way of fighting Each man served for 25 years, but auxiliaries were not given any land when they retired. From the 3rd century, there were also irregular units of mercenaries, hired from the local Britons. They were called numeri. When the Roman army left Britain in the late 4th & early 5th centuries, the auxiliaries went too. The Roman way of life then fell apart.