It was under Augustus that the classical “legion” system that is so well known today came into common use. He organized the armies of Rome into an effective, conquering fighting force that would not be greatly changed until the reforms of Emperor Diocletian some 300 years later.
Under Augustus, the legions became fighting forces of heavy infantry who were professionals (Roman citizens), and light infantry, archers, and cavalry who were auxiliary (non-citizens.) A legion was comprised of 5-6000 citizen soldiers, flanked by cohorts of various types of auxiliary troops that numbered around the same; giving the legion a total number of around 10,000.
Contubernium (Tent Group) - consists of 8 men.
Centuria (Century) - consists of 10 Tent Groups, for a total of 80 men. Commanded by a Centurion.
Cohors (Cohort) - consists of 6 Centuries, for a total of 480 men, not including officers. Additionally the First Cohort consisted of only 5 double-strength centuries, (making it 160 per Century).
Legio (Legion) - consists of 10 cohorts. In addition, every legion had an attachment of cavalry attached to it known as Eques Legionis to be used as scouts and messengers.
So, in total: the First Cohort totals 800 (with 5 double-strength Centuries numbering 160 men each) + 9 normal-strength Cohorts (each Cohort with 6 Centuries of 80 men) = 4,320, plus an additional 120 cavalry for a grand total of 5,240 men without officers included. In AeRO, to make numbers easier to understand, we round legions to 10,000 men strong. A standard legion will have 5,300 standard, citizen legionnaires (officers included) with 4,700 auxiliaries. A typical consular army (a field army) used for warfare would have at least two full-strength legions with two legions of Auxiliaries, totally around 40,000 men. There would be one Legatus (usually the governor of the province) in command of the field army, with other legates in command of individual legions.
Senior Officers - Typically men of aristocratic, Patrician or Equestrian standing. They receive the highest pay.
- Legatus Legionis - The overall Legionary commander. This post is usually appointed by the emperor. A Legatus must be a former Tribune and holds command for 4 years, although extensions are possible and often used.
- Tribunus Laticlavius - Appointed by the Emperor or the Senate. Though generally quite young and less experienced than the Tribuni Angusticlavii, he serves as second in command of the legion, behind the Legate.
- Praefectus Castrorum - The camp Prefect. Typically the Prefect is a man who serves through the ranks of Centurions and is promoted. Is third in command of the legion.
- Tribuni Angusticlavii - Each legion has 5 military tribunes of Equestrian class citizens. They are in many cases career officers and serve many of the important administrative tasks of the Legion. However, during engagements, they still serve in a full tactical command. Two of these five, however, are -- like the Laticlavii above -- appointed at a young age.
- Primus Pilus - The "First File" is the commanding centurion of the First Cohort and the senior centurion of the entire Legion. Service in this position also allows entry into the Equestrian social class upon retirement.
Mid-Level Officers - Always men of lower Equestrian standing or citizens who managed to work their way through the ranks.
- Centurions - Each Legion has 59 centurions, one to command each centuria of the 10 cohorts. They are the backbone of the professional army and are the career soldiers who run the day to day life of the soldiers as well as issuing commands in the field. They are generally moved up from the ranks, but in some cases could be direct appointments from the Emperor or other higher ranking officials.
- Pilus Prior - The commander of the first cohort of each Centuria (except the first). Often moved up through the ranks based on experience.
Low-Level Officers - Again, typically these are men of Equestrian class, though Citizens can attain these positions as well.
- Aquilifer - A single position within the Legion. The Aquilifer is the Legion's Standard or Eagle bearer and is an enormously important and prestigious position. The next step up is a post as a Centurion.
- Signifer - Each Centuria has a Signifer (59). He is responsible for the men's pay and savings, and the standard bearer for the Centurial Signum, a spear shaft decorated with medallions and often topped with an open hand to signify the oath of loyalty taken by the soldiers.
- Optio - One for each Centurion (59), they are appointed by the Centurion from within the ranks to act as his second in command.
- Tesserarius - (Guard Commander) Again there are 59 of these, or one for each Centuria. They act in similar roles to the Optios.
- Cornicen - (Horn blower) They work hand-in-hand with the Signifer drawing the attention of the men to the Centurial Signum and issuing the audible commands of the officers.
- Imaginifer - Carries the Standard bearing the image of the Emperor as a constant reminder of the troop's loyalty to him.
Rank and File Soldiers - Men of almost exclusively Citizen standing, though at times freedmen are enlisted.
- Immunes - These are trained specialists, such as surgeons, engineers, surveyors, and architects, as well as craftsmen. They are exempt from camp and hard labor duties due to the nature of their work, and earn slightly more pay.
- Discens - Milites in training for an immunes position.
- Munifex/Milites - The basic, private level foot-soldier.
- Tirones - The basic new recruit. A Tirones can take up to 6 months before becoming a full Milites.
Written by Chris.