A republic-era legion contained 4,000 – 5,000 regular troops called legionaries, divided evenly among ten units called maniples[1]. Two officers called centurions, one junior and one senior, commanded each maniple with help from assistants who acted as quartermasters. Soldiers were assigned to these units according to their age and experience, so that each fought in a unit of his agemates – except the youngest group, who were distributed among the other maniples.
Another 4,000-5,000 troops called auxiliaries followed each legion, filling the roles of archers, cavalry, and light infantry. Most of these were foreigners or other non-citizens, fighting in exchange for citizenship. Including these, a legion stood about 10,000 men strong.
A legion’s clear chain of command ensured every soldier knew his place, and minimized confusion during battle. Less confusion not only meant fewer casualties, but also made more advanced tactics practical. A larger tactical playbook made the legions more flexible, less predictable, and far more deadly to their enemies.
Roman Weapons and Soldiers
The members of a legion were career soldiers who served for sixteen to twenty years. All of them full citizens of Rome, they fought the Empire’s battles, and built the roads, bridges and forts which won her wars. Their training focused on co-operation and building key structures as well as fighting in close-quarters combat. All legionaries fell into one of four groups: velites (untested youths), hastati (regulars), principles (soldiers in their prime), and triarii (aging veterans).
For protection, non-velites carried four-foot tall rectangular shields which covered most of their bodies, and wore bronze helmets and shin-armor. Body armor varied. For attack, they employed a short, broad sword and two of a throwing spears called pila (sing. pilum). The pilum bent sideways after it struck, which stopped the enemy from re-using it and disabled any shield or foot it lodged in. Velites made do with a smaller circular shield, two throwing spears, and a sword.
Roman legions also employed advanced siege machines, the artillery of their time, whenever practical. Many were only useful against fortifications, but the most famous of these machines, a giant crossbow called the ballista, was also used in some field engagements. This fired a foot-long projectile which could kill from a thousand feet away, making it a fearsome weapon.
Regardless of equipment, any mass of soldiers can become either an army, or an armed mob. Of the two, armies win battles - often by butchering armed mobs. The organization and discipline which kept Romans fighting in armies instead of mobs probably saved the lives of more legionaries than any body armor, and the legion’s tactical flexibility caused more enemy deaths than any machine like the ballista.
Sources
Polybius. The Rise of the Roman Empire. Translation by Scott-Kilvert, Ian. New York: Penguin Group, 1979. Penguin Press, Inc., New York 10014.
Scarre, Chris. The Penguin Historical Atlas of Ancient Rome. New York: Penguin Books, 1995. Penguin Putnam inc., New York 10014.
