Organization of the Roman Imperial Legion
In the Roman army, a full strength legion was officially made up of 6,000 men, but typically all legions were organized at under strength and generally consisted of approximately 5,300 fighting men including officers.
It is difficult to determine whether non-combatants like field surgeons and clerks were included in the 5,300 or helped bring the total number of men up to the official 6,000.
In this page, we look at the overall fighting strength of a Roman Imperial legion, how it was organized, and the many different ranks of those within it.
The basic structure of the army is as follows:
- Contubernium (tent group): consisted of 8 men.
- Centuria (century): was made up of 10 contubernium with a total of 80 men commanded by a centurion.
- Cohorts (cohort): included 6 centuriae or a total of 480 fighting men, not including officers. In addition, the first cohort was double strength but with only 5 centuriae instead of the normal 6.
- Legio (legion): consisted of 10 cohorts.
Additionally each Legion had a 120 man Alae (cavalry unit) called the Eques Legionis permanently attached to it possibly to be used as scouts and messengers.
Total Fighting Strength of a Legion
The First Cohort totaling 800 men (5 double-strength centuries with 160 men each) 9 Cohorts (with 6 centuries at 80 men each) for a total 4,320, and an additional 120 man cavalry for a grand total of 5,240 men not including all the officers.
The basic designation of the 10 cohorts was the same throughout all the Legions. They were arranged in battle so that the strongest and weakest units would be mixed throughout the formation maximizing moral and effectiveness.
- Cohort I: Was made up of the elite troops. Its direct commander was the Primus Pilus, the highest ranking and most respected of all the Centurions.
- Cohort II: Consisted of some of the weaker or newest troops.
- Cohort III: No special designation for this unit.
- Cohort IV: Another of the four weak cohorts.
- Cohort V: Again, no special designation.
- Cohort VI: Made up of "The Finest of the Young Men".
- Cohort VII: One of the four weak cohorts and a likely place to find trainees and raw recruits.
- Cohort VIII: Contained "The Selected Troops".
- Cohort IX: One of the four weak cohorts and a likely place to find trainees and raw recruits.
- Cohort X: Made up of "The Good Troops".
Roman Legionary Ranks
The following list indicates ranks from highest command to lowest common soldier:
Senior Officers of the Roman Legion
The overall Legionary commander. This post was generally appointed by the emperor, was a former Tribune and held command for 3 or 4 years, although could serve for a much longer period. In a province with only one legion, the Legatus was also the provincial governor and in provinces with multiple legions, each legion has a Legatus and the provincial governor has overall command of them all.
Named for the broad striped toga worn by men of senatorial rank. This tribune was appointed by the Emperor or the Senate. Though generally quite young and less experienced than the Tribuni Angusticlavii, he served as second in command of the legion, behind the Legate.
The camp Prefect. Generally he was a long serving veteran who had been promoted through the ranks of the centurions and was 3rd in overall command.
Each legion had 5 military tribunes of equestrian (knight) class citizens. They were in many cases career officers and served many of the important administrative tasks of the Legion, but still served in a full tactical command function during engagements.
The "First File" was the commanding centurion of the first cohort and the senior centurion of the entire Legion. Service in this position also allowed entry into the equestrian social class upon retirement.
Mid-Level Officers in the Roman Legion
Each Legion had 59 or 60 centurions, one to command each centuria of the 10 cohorts. They were the backbone of the professional army and were the career soldiers who ran the day to day life of the soldiers as well as issuing commands in the field. They were generally moved up from the ranks, but in some cases could be direct appointments from the Emperor or other higher ranking officials.
The cohorts were ranked from the First to the Tenth and the Centuria within each cohort ranked from 1 to 6, with only 5 Centuria in the First Cohort (For a total of 59 Centuria and the Primus Pilus). The Centuria that each Centurion commanded was a direct reflection of his rank. (Command of the First Centuria of the First Cohort was the highest and the 6th Centuria of the 10th Cohort was the lowest). The 5 Centurions of the First Cohort were called the Primi Ordines, and included the Primus Pilus.
The commander of the first cohort of each Centuria (except the first), with the following titles for the Centurions in sequence throughout each Centuria.
- Pilus Posterior
- Princeps Prior
- Princeps Posterior
- Hastatus Prior
- Hastatus Posterior
Low-Level Officers in the Roman Legion
The Principales would be the equivalent of modern day non-commissioned officers and had the following rank structures from highest to lowest:
A single position within the Legion. The Aquilifer was the Legion's Standard or Eagle bearer and was an enormously important and prestigious position. The next step up would be a post as a Centurion.
Each Centuria had a Signifer (59). He was 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. It was this banner that the men from each individual Centuria would rally around. A soldier could also gain the position of Discentes signiferorum, or standard bearer in training.
One for each Centurion (59), they were appointed by the Centurion from within the ranks to act as his second in command.
Tesserarius (Guard Commander)
Again there were 59 of these, or one for each Centuria. They acted in similar roles to the Optios.
Cornicen (Horn Blower)
They worked hand in hand with the Signifer drawing the attention of the men to the Centurial Signum and issuing the audible commands of the officers.
Carried the Standard bearing the image of the Emperor as a constant reminder of the troop's loyalty to him.
The Rank and File of the Roman Legion
These were trained specialists, such as surgeons, engineers, surveyors, and architects, as well as craftsmen. They were exempt from camp and hard labor duties due to the nature of their work, and would generally earn slightly more pay than the Milites.
Milites in training for an immunes position.
Munifex (or Miles Gregarius)
The basic private level foot soldier.
The basic new recruit. A Tirones could take up to 6 months before becoming a full Milites.
Basic Legionary Equipment
On the march the Legionary could carry between three and fourteen day's worth of rations, a saw, a wicker basket, a piece of rope or leather, a shovel, a waterskin, a sickle and a pickaxe. Each of these items, aside from the pickaxe which was worn on the belt, was carried on a forked pole introduced by Gaius Marius called the pila muralia, which earned his men the nickname Marius' Mules.
There is some discrepancy over what was actually carried and the possible total weight. At times, some items may have been transported in wagon trains or on mules such as the legionaries' tents and millstones for grinding the corn rations. It has been estimated that a legionary could carry anywhere from 66 lbs. (30 kgs) to over 100 lbs. (45 kgs) of gear and weapons, with Roman armor and shields being particularly heavy.
A centurion's equipment was notably different from that of a legionary. He wore a transverse, side to side, crest along his helmet that would serve as an easily recognized point of reference for the men. The crest was made either of feathers or horsehair and colors could signify various ranks. Rather than the Lorica Segmentata of the Legionary, they would wear either chain or scale. It was generally about waist length with a lower edge similar to the muscled cuirass. The armor and helmet could be silver-plated as well. He did not wear the apron like the Legionary but had a double-pleated kilt like piece. They also wore a cloak, of fine material, which hung from the left shoulder and a very ornate belt.
Additionally the wearing of bronze greaves on the shins set them apart from the rank and file. They generally wore their swords on the left and daggers on the right, opposite of the common soldiers. They carried a Vitis, vine staff, in his right hand as a symbol of his rank. It was made of grapevine and about 3 feet long.
Officers could, of course, dress very differently from anyone else and there seems to be set pattern to the styles. They did have very fine dyed cloaks of various colors to signify rank. They generally wore a muscled cuirass and used a parazonium instead of a gladius; both described below.
Did you know...
Until the reign of Septimius Severus, soldiers were forbidden to be legally married while serving, though of course many had local girlfriends, common-law wives, and children.
Did you know...
The equipment to the legionaries was remarkably uniform throughout the empire and it is possible that there were large centres in Gaul and North Italy for the mass manufacture of helmets, armor and weapons.