From a small village by the Tiber River, Rome rose to become one of history’s greatest empires, largely due to the strength of its legions. The key to Rome’s glory was its tightly organized system, where every soldier, from recruit to legion commander, had a specific role. This hierarchy was a critical factor in Rome’s ability to outmatch and overpower its rivals for centuries.
The Roman army is famed as an efficient war machine thanks to its structured organization and rigorous discipline. Below are the ranks in Rome’s military system. In this article, Thefactsofwar will join readers in exploring the ranks of the Roman army during the peak of the empire’s power.
Structure of the Roman Legion
The Roman army evolved significantly over centuries, from a temporary militia to a Greek-inspired phalanx, and later to the maniple formation during the Middle Republic. By the late Republic, consul Gaius Marius faced a manpower shortage and abolished the land ownership requirement for military service.
With this change, any free Roman citizen, regardless of wealth or status, could join the army. Becoming a soldier became a professional career choice. This allowed Marius to build a new army structure, refined over time and formalized under Augustus.
The core of the Roman army was its heavy infantry. The smallest unit was the contubernium, eight men sharing a tent. Ten contubernia formed a century (company), six centuries made a cohort (battalion), and ten cohorts comprised a legion, the largest unit in the Roman army. A standard legion also included 120 cavalry and support forces, though exceptions to this rule occasionally existed.
For example, the first cohort of each legion had five centuries instead of six, with each century doubled in size to 160 men rather than 80. However, it remains unclear whether this was standard across all legions or applied only to certain units due to specific circumstances.
Senior Officers in the Roman Army
At the top of the legion’s command was the legatus legionis (general), a Senatorial class member appointed by the emperor. Typically over 30, he held the post for about four years, though longer service was possible if needed. His status was reflected in his residence at camp, the praetorium, which included rooms for family, servants, and even gardens or luxurious amenities. As a senator, he was entitled to an escort of five lictores carrying fasces—symbols of authority.
In battle, the legatus wore elaborate armor, a crested helmet, a red cloak, and a belt called the paludamentum and cincticulus, making him easily recognizable to troops. Beyond military duties, he held political roles. In a province with one legion, he also served as governor. If multiple legions were present, each had its own legatus, all under the provincial governor’s authority.
Below the legatus legionis was the tribunus laticlavius (broad-stripe tribune). Typically in their late teens or early 20s, they were identified by a wide purple stripe on their toga, signifying Senatorial status. Though second-in-command, the tribunus laticlavius had no specific role, mainly gaining military experience—a key step in a young Roman’s political career. Appointed by the Senate or emperor, they stood out with white cloaks and more lavish camp quarters than regular soldiers.
The third-highest rank was the praefectus castorum (camp prefect). Unlike other commanders, he often rose from the lower classes as a career soldier, typically selected from the primus pilus (senior centurion).
Having spent much of his life in the military, he possessed practical experience the legatus and tribunus laticlavius lacked. His primary role was overseeing the legion, handling administration and daily operations to maintain efficiency. In the legatus’s absence, he assumed legion command. He also managed training and kept troops combat-ready.
Under these three were five tribuni angusiclavii (narrow-stripe tribunes) from Rome’s Equestrian class. Identified by a narrow purple stripe on their toga, symbolizing their social rank, this role was a launching pad for potential political careers. Some stayed with the legion as career soldiers. They lacked direct command over the legion, instead performing administrative tasks like overseeing guard shifts or serving on disciplinary councils.
Centurions in the Roman Army
The most famous and perhaps vital rank in the Roman army was the centurion (company commander). These were professional officers, mostly from lower classes, rising through the ranks, though some were chosen from the Equestrian class. Each legion had 59 centurions, each commanding a century of 80 soldiers.
Centurion ranks varied, with the highest being the primus pilus (first spear). He commanded the first century of the first cohort—a double-sized unit of 160 men—and was often next in line for camp prefect. If not already an Equestrian, the primus pilus was ennobled upon retirement. The five other centurions in the first cohort, called primi ordines, outranked other centurions in the legion.
Remaining centurions bore titles tied to the Roman army’s history from the Middle Republic and ancient maniple formation. These included pilus prior, pilus posterior, principes prior, principes posterior, hastatus prior, and hastatus posterior, in descending order. The pilus prior commanded a cohort’s first century and held authority over the entire cohort in battle, outranking other centurions in that cohort.
A centurion’s specific status depended on the century he led. The centurion of the first century outranked the second’s, and so on. Similarly, the first cohort outranked the second, down to the tenth. In a legion, the primus pilus was the senior-most centurion, while the commander of the sixth century in the tenth cohort was the lowest.
Most centurions earned their rank after years of service, rising through the ranks, though some were directly appointed by the emperor, Senate, or senior officials. Literacy in Latin was mandatory, as they needed to read and relay written orders.
In peacetime, centurions maintained discipline and combat readiness. Their symbol of authority was a vine staff (vitis), used to punish soldiers when needed. One centurion, nicknamed “Cedo Alteram” (give me another), was famed for breaking his staff on soldiers’ backs and demanding a new one. He was killed in a mutiny.
In battle, centurions were recognizable by their transverse-crested helmets and swords worn on the left hip—unlike regular soldiers, who wore them on the right. They also donned more elaborate armor, including metal greaves and belts adorned with medals and rewards earned over their careers.
Their primary duty was leading soldiers—not just by orders but by example. Positioned at the front left of the century, they were the first to charge in every attack and the last to retreat. This role often led to high casualty rates throughout their service.
Junior Officers in the Roman Army
Below centurions were the principales, akin to modern non-commissioned officers. The most significant was the optio. Chosen by the centurion from the ranks, the optio was the century’s second-in-command, assisting with administrative tasks.
The optio also oversaw training and discipline. In battle, he stood at the rear right of the formation, opposite the centurion, ensuring ranks held firm. He wielded a wooden staff—his symbol of office—to prod and encourage soldiers to stay in line. If the centurion fell, the optio took command.
Each century also had a tesserarius, named after the tessera wax tablet used for passwords. He safeguarded and distributed passwords to necessary soldiers and supervised guard duties. In battle, he stood at the rear left, aiding the optio in maintaining order. Under him was the decanus, leading the eight-man contubernium (tent group), typically the most experienced member.
Every century had a signifer, sometimes called a vexillarius, who carried the signum—a spear adorned with medals, often topped with a metal hand, symbolizing the oath of loyalty to the emperor each soldier swore. The signum was the century’s rallying point, a vital marker amid battle chaos. Signifers were identified by the animal hides they wore as a badge of office.
Beyond the battlefield, signifers managed soldiers’ pay and savings accounts. They worked closely with the cornicen, who carried a large bronze horn to relay orders in battle or summon attention.
Each legion also had an imaginifer, bearing a standard with the emperor’s image—a constant reminder of the soldiers’ oath. Additionally, the aquilifer carried the legion’s golden eagle, one of the army’s most prestigious roles. Losing this symbol was a great dishonor. Emperor Augustus claimed recovering eagles lost to Parthia at Carrhae was among his greatest achievements, underscoring the aquilifer’s importance.
In status, the aquilifer ranked between the optio and centurion. Advancing to centurion was often the next career step for an aquilifer.
Other Ranks and Auxiliary Forces
Beyond specific ranks, the Roman legion had a general class called immunes. These were specialists—blacksmiths, carpenters, siege engine operators, engineers, medics, clerks, and more. Due to their skills, they were exempt from most grueling daily tasks like guard duty or sanitation. Immunes might earn slightly higher pay than regular soldiers. Those training to become immunes were called discens.
Below all ranks was the munifex, the common soldier. Forming the bulk of the army, they earned the lowest pay and performed the backbreaking, repetitive tasks keeping the army running. Yet, with bravery, skill, and dedication, a soldier could catch a superior’s eye and rise, gaining status and wealth, potentially even reaching camp prefect.
A lower tier still was the triones, recruits. During months of training, they faced strict discipline and learned essential soldiering skills. This included marching in formation, digging trenches, building stockade walls around camps—done nightly on the march—plus running, swimming, basic riding, and mastering weapons like the pilum (javelin), alongside relentless sword-and-shield drills.
Training weapons were twice the weight of real ones to build strength. Upon completing training, triones became munifex, assigned to a legion, and began their 25-year service term.
Besides Roman soldiers, the army employed auxiliares (auxiliaries), non-citizens fighting in legions for citizenship upon completing service. Auxiliaries could be infantry, cavalry, or both in mixed units.
Cavalry were organized into alae (wings), comprising 16 turmae (troops), led by a praefectus alae. Each turma had 32 cavalrymen, commanded by a decurion, with a duplicarius as deputy. Auxiliary infantry were arranged in cohorts and centuries, with ranks and roles mirroring regular legionaries.
This hierarchy existed during the Principate, Rome’s peak power period. During the third-century crisis, the Roman army was restructured, phasing out some old ranks and roles for new ones better suited to Rome’s defensive strategy. Regardless of changes, the legion’s organization remained the bedrock of Rome’s strength, from its early days to the empire’s fall.
Conclusion
In Summary, the Roman army was not just a mighty military force but a symbol of organization, discipline, and remarkable strategic evolution. From its clear hierarchy and flexible legion structure to the roles of individuals from recruit to commander, it forged a great war machine that enabled Rome to dominate for centuries.
Thefactsofwar hopes this article has offered readers deeper insight into how the Roman army operated and its crucial role in building one of history’s greatest empires. We also aim to spark interest in the values and lessons we can glean from their exceptional organization and leadership.
Translated by: Minh Tuan
Source: thecollector.com – Roman Military Ranks: From Legionary to General
