Roman Legion

 

The Roman Army comprised a series of legions, each consisting of around 5,280 men (excluding officers).

• The basic structure of the legion was the Contubernium (the tent group): 8 men (roughly a squad).

• The Centuria (Century) consisted of ten Contubernium (80 men) (roughly a company).  Its commanding officer was called Centurion.

• The Cohort included six Centuriae (480 fighting men (not including officers).  A cohort was a rough equivalent to a modern-day battalion.  The first cohort, however, was double strength (960 men) (two battalions), but with five centuries instead of the normal six.

• Generally, a legion consisted of ten Cohorts plus 120 Alae (cavalry).  A Roman Legion was roughly equivalent to a modern U.S. Brigade.

Cohort I was made up of the legion’s most elite troops.  Its commander was called Primus Pilus (First Spear), the highest ranking and most respected of all centurions.  Primus Pilus was the second in command of the legion.

Cohorts III, V, VI, VIII, and X were the strongest (most experienced) legionaries.

Cohorts II, IV, VII, and IX were inexperienced men, soldiers in training, or raw recruits.

Beginning around 107 B.C., the Roman Senate demanded a more professional army.  The Senate required a senior officer to serve in the overall command of a legion.  He would be called Legatus — the Roman version of Commanding General.  Most of Rome’s provincial governors also served as Legates, exercising overall command authority over one or more legions assigned to his province.  A Legate’s relative seniority as a military commander depended on the size of his command.

Each legion had five to six military tribunes (Tribunus Militum).  They were mid-range officers, subordinate to the Legate, but senior to centurions.  Generally, young men of Equestrian rank served as military tribunes as a stepping-stone to the Roman Senate.  One tribute served as second in command under the Legate.  He was called the broad stripe tribune (Tribunus Laticlavius).  A wide stripe appeared on his tunic (and toga).  Subordinate tribunes were referred to as thin-stripe tribunes (Tribuni Angusticlavii).  Beyond their tactical responsibilities in combat, Tribunes performed certain administrative tasks — likely like the modern-day function of adjutant, operations, training, logistics, and signals.

Third in command of the legion was the Camp Prefect (Praefectus Castorum).  This individual served a critical function in the command.  He was likely trained as an engineer, a long-serving veteran promoted through the ranks of centurions.

Legions were known to march 30 to 50 miles in a single day.  At the end of the day, legions set up a defensive perimeter using available woodland materials.  The temporary enclosure looked like a Hollywood-style fort, with wood pike walls, an outside moat-like trench, elevated sentry stands for observation, two guarded and reinforced gates, camping areas large enough to accommodate up to six thousand men, and a corral for horses and other pack animals.  The legionary enclosure had to be set up before the men were allowed to have their evening meal.

The next morning, the entire defensive enclosure was disassembled before dawn, and the men prepared to step out on the next day’s march.  The camp prefect commanded the legion in the absence of the Legate and Tribunus Laticlavius.

Each legion had around sixty centurions — one to command each Centuria.  Centurions were the backbone of the professional army, somewhat like company-grade officers in the modern world.  The Centuria that each Centurion commanded reflected his rank.  Command of the First Centuria of the First Cohort was the highest-ranking Centurion.  He was called Primus Pilus (First Spear).  Some today equate this man as roughly equivalent to a major.  Successful service as a Primus Pilus opened the door to the advancement into the equestrian social class (upon retirement).  Most centurions earned promotions from the ranks of common soldiers, who generally served 25 to 30 years of service before they were eligible for retirement/discharge.

The legion

Sources:

1. Rich, J.  Military Organization and Social Change, War and Society in the Roman World.  Graham Shipley (Ed.) Leicester-Nottingham Studies in Ancient Society, 1993.

2. Dando-Collins, S.  Caesar’s Legion: The Epic Saga of Julius Caesar’s Elite Tenth Legion and the Armies of Rome.  Wiley Publishing, 2002.

3. United Nations of Rome Victrix (UNRV): History of Ancient Rome (online)