Roman Legion - Overview of Typical Organization & Strength

Overview of Typical Organization & Strength

Because legions were not standing units until the Marian reforms (c. 107 BC), and were instead created, used, and disbanded again, several hundred legions were named and numbered throughout Roman history. To date, about 50 have been identified. In the time of the Early Roman Empire, there were usually about 25–35 permanent standing legions.

A legion consisted of several cohorts of heavy infantry known as legionaries. It was almost always accompanied by one or more attached units of auxiliaries, who were not Roman citizens and provided cavalry, ranged troops and skirmishers to complement the legion's heavy infantry. The recruitment of non-citizens was rare but appears to have occurred in times of great need; For example Caesar appears to have recruited the Legio V Alaudae mostly from non-citizen Gauls.

The size of a typical legion varied throughout the history of ancient Rome, with complements of 4,200 legionaries and 300 equites (drawn from the wealthier classes - in early Rome all troops provided their own equipment) in the republican period of Rome, (the infantry were split into 30 maniples of 120 legionaries each), to 5,200 men plus auxiliaries in the imperial period (split into 10 cohorts, 9 of 480 men each, plus the first cohort holding 800 men).