Legion

A military unit forming the backbone of the Roman army, nominally composed of 6,000 soldiers, and divided up into 10 cohorts, with each cohort containing 6 centuria. The centurion thus nominally commanded about 100 men, and there were 60 centurions in a legion. Each was based at a legionary fortress, a larger and more permanent version of the Roman military camp. Numbers within a legion changed again under the Empire, and from Diocletian onwards (284-316 AD), the legions were increased in number but reduced in size. Each legion was given the standard of the eagle, an identifying number, and an honorific title, often based upon the name of the founder.

The principal organizational unit of the Roman army, composed of Roman citizens. The legion changed size and character over the Roman period, ranging from a unit of 3,000 with a property qualification under the early kings, to one of6,000 in the final century of the Republic. Numbers changed again under the Empire, and from Diocletian onwards (284316 ad) the legions were increased in number but reduced in size. Each legion was given the standard of the eagle, an identifying number — there were more than 30 under Severus (193211) — and an honorific title, often based upon the name of the founder. The legion was typically subdivided into ten cohorts, and each cohort into six centuries.