The principal heavy-infantry formation of the Roman army and a central institution of Roman expansion.
Overview
The legion was the core formation of Roman land warfare. Its size and internal organisation changed over time, but it combined citizen manpower, disciplined training, engineering capacity, and a flexible command structure.
Why It Matters
By the late Republic, legions could become closely attached to successful commanders. Long campaigns, expectations of land, and dependence on generals for rewards contributed to the militarisation of political conflict.
In Roman Practice
A legion was divided into smaller tactical units and supported by allied or auxiliary troops. It was also a marching community with officers, engineers, servants, animals, and an extensive supply system.