10 Interesting Facts On The Ancient Roman Army

The formation of the Roman Army has been dated back to 753 BCE and it was in existence till 1453 CE. Thus it lasted for a period of more than 2,000 years. During this period, it underwent numerous permutations and combinations in composition organization, equipment, tactics and more. However, it was able to conserve a core of lasting traditions. Starting from a levies system, the Roman army ultimately evolved into a standing professional army. It was adept at battle in the open field and in siege warfare while being exposed by tactics like guerrilla warfare. It used several formations including triplex acies, testudo and the wedge. Moreover, the Roman army employed a measured approach during battle and is infamous for institutionalizing brutality. Here are 10 interesting facts about the history, structure, formations, military tactics, strategy, strengths and weaknesses of the Roman army as well as about its greatest defeat and victory.


The legion was the largest unit in the Roman army. The term legion is derived from the Latin word legio, which means draft or levy. The legion evolved from around 3,000 men in the Roman Republic to over 5,200 men in the Roman Empire. A legion was divided into cohorts of around 500 men. A cohort comprised of centuries. A centuria was named so as it originally consisted of a hundred soldiers. However, later it contained 60 to 80 soldiers distributed among 10 contubernia of 8 soldiers. Contubernium was the smallest unit in the Roman legion. Its soldiers lived in the same tent while on campaign or the same bunk room in barracks. Until the middle of 1st century CE, a legion comprised of 10 cohorts. This was later changed to nine cohorts of standard size, each with six centuries of 80 men with the first cohort being of double strength, five double-strength centuries with 160 men each. However, by 4th century CE, the legion was a much smaller unit of about 1,000 to 1,500 men; and there were more of them

Organization of Roman legion
Diagram showing organization of the late Republic legion


The Early Roman army (500 BC to 300 BCE) was based on an annual levy. Warfare during this time primarily involved small scale plundering raids. In the Mid-Republic Period (300 BC – 88 BCE), the Romans maintained the levy system but adopted the manipular organization for their legions, in which it was organized into four lines, starting at the front: the velites, the hastati, the principes and the triarii. The Late Republic Period (88 to 30 BCE) saw an increasing number of recruits being volunteers who signed up for 16-year terms as opposed to the max 6-year terms of conscripts.

Organisation of the Manipular Legion
Organisation of the Manipular Legion

In Imperial Rome (30 BCE – 284 CE), the conscription based system was entirely replaced by a standing professional army of mainly volunteers serving standard 20-year terms in addition to 5 year as reservists. However, many served up to 30 to 40 years on active duty. The Late Roman Army (284 – 476 CE) returned to regular annual conscription of citizens. It also started admitting large numbers of non-citizen barbarian volunteers. However, the soldiers remained 25-year professionals and the short term levies system was not returned to.


Most soldiers in the Roman army were primarily interested in receiving large pension amounts and a piece of land on retirement. As a result, their actual engagement of the enemy was measured and cautious rather than being that of seeking glory as a warrior. The generals mainly concentrated on maintaining close-knit formations and protecting individual troops. A Roman legion consisted of several cohorts of heavy infantry known as legionaries. These were always accompanied by one or more attached units of auxiliaries, which were non-Roman citizens and provided cavalry. Here is how a scene of battle involving the Roman army would typically unfold. Light troops were the first to engage with the enemy. This was followed by the cavalry being used to screen the central core from envelopment. The heavy infantry ultimately joined the battle as the gap between the contenders closed.

Roman legionaries
Relief scene of Roman legionaries


In his book The Grand Strategy of the Roman Empire, noted political scientist Edward Luttwak proposes that the Romans had a grand military strategy. He divided this strategy into three phases. The first phase was from from Augustus to Nero (27 BCE – 68 CE). In this phase, the allies of Rome provided a buffer along the perimeter of the empire allowing Rome’s military forces to be positioned at strategic points. The second phase was from the Flavians to the Severan emperors (69 – 235). In this phase, the Roman empire became a fortress with a precise perimeter. The aggressors were dealt beyond the boundaries of the empire to ensure peace and prosperity within the empire. The last phase is from 284 CE to 305 CE. In this phase, the Romans allowed the aggressors to enter their territory through predetermined routes and contained them through point defenses. Though Luttwak’s book was a success, some have questioned his analysis pointing out several factors including that power in Rome resided with one individual and hence a grand strategy could not be sustained.

The Grand Strategy of the Roman Empire (1976)
The Grand Strategy of the Roman Empire (1976) – Edward Luttwak


The Roman legion was adept at fighting battles in open fields. In open fields, they had well-rehearsed tactics and formations to execute and crush their enemies with maximum effectiveness. It was rare for the Romans to lose the battle in the open. Their enemies at times realized this and devised other methods to confront them. In fact, some of the most humiliating defeats of the Roman army came as a result of their opposition using ambushes. Romans never used ambushes as a military tactic. Guerrilla warfare was an effective tactic against the Roman army. This involved launching fast attacks against Roman soldiers from the flanks before quickly retreating into areas where the Romans would have difficulty following the enemy. Caratacus, a British war chief, effectively employed guerrilla warfare against the Romans for around 8 years. Moreover, the Goths and the Huns later used guerrilla warfare to force the Romans on the defensive.


Though the Romans preferred warfare in open field, as the necessity arose they also became adept in siege warfare. In a typical Roman siege, if an initial attack failed to bring immediate victory, forces were sent to surround the city. This included a naval blockade. This was done to force the opposition to surrender due to starvation, lack of water etc. To prepare for an attack, the Roman army built siege towers whose heights were equal or a bit more than the walls of the city. Siege towers protected the army and ladders while they approached the defensive walls. They also allowed the archers to stand on top of the tower and shoot arrows into the fortification.

Roman Siege Tower
Depiction of a Roman Siege Tower

Roman siege weapons include the ballista, a catapult used for hurling large stones; the carroballista, which fired heavy arrows, bolts or smaller stones and had two arms like a crossbow; and an onager, a small catapult. Apart from siege towers and sophisticated weapons, Romans remarkable success at sieges was enabled by superior logistics to ensure long-term supply and mastery of the seas.


The Roman army used various formations to face their enemy including the triplex acies (triple battle order), the testudo (tortoise) and the wedge. In triple battle order, the soldiers were arranged in three ranks: the least-seasoned men, hastati, made up the front rank; the principes were in the second rank, and the veteran triarii in the third and final rank. The three lines had alternating gaps to allow even more room for maneuver. When facing defeat, the first two lines fell back on the triarii to reform the line to allow for either a counter-attack or an orderly withdrawal. The testudo formation was a shield wall formation in which the men would align their shields to form a packed formation covered with shields on the front and top. The testudo gave protection from arrows and other missile weapons while offering consistent defensive strength against opposing infantry. The wedge was an offensive military formation. Formed like a triangle, it was used to cut through enemy lines.

Roman Testudo formation
Testudo formation of the Roman army


The Second Punic War was the second of three wars between Carthage and the Roman Republic. The most famous battle of the Second Punic War was the Battle of Cannae, which took place on August 2, 216 BCE. In the battle, the army of Carthage, under the famous general Hannibal Barca defeated the larger army of the Roman Republic under consuls Lucius Aemilius Paullus and Gaius Terentius Varro. Hannibal used the double-envelopment tactic against the Roman army surrounding most of them and then slaughtering them. It is estimated that the Carthaginians killed at least more than 40,000 Romans in a day, amounting to more than 80% of the Roman army. This makes the battle one of the most lethal single day’s fighting in history. The Battle of Cannae is widely considered as one of the greatest strategical victories in military history as well as one of the worst defeats in the history of the Roman army.

The Battle of Cannae
Painting by John Trumbull depicting the Battle of Cannae


The Third Punic War was the last military engagement between Carthage and the Roman Republic. The Battle of Carthage proved to be the primary battle of the Third Punic War. Carthage had surrendered in 149 BCE handing over its hostages and arms. However, the Romans demanded complete surrender of the city, which the Carthage council refused by a vote of one. Led by the young and popular consul Scipio Aemilianus, the Roman army then began a siege operation, starting sometime in 149 or 148 BCE. Behind the walls the Carthaginians transformed the city into a huge arsenal producing daily 300 swords, 500 spears, 140 shields and over 1,000 projectiles for catapults. However, after a period of two years, the Romans won the Battle of Carthage. They sacked and completely destroyed the city. Moreover, an estimated 50,000 surviving inhabitants of Carthage were sold into slavery. Battle of Carthage has been called probably the first genocide in history.

The Battle of Carthage
Painting depicting the Battle of Carthage


Rather than inculcating defensive strategies, Romans were known to usually be on the attacking front by fostering violence as a culture. This paved way for violence to be institutionalized, which was further promoted through the lethal gladiator games. Apart from this, soldiers were encouraged to take part in brutal strategies and massacres. Roman political leaders gave more leeway to soldiers than any other civilization. Soldiers were allowed to rape women and carry out massacre on foreign lands. But Roman soldiers themselves were also subjected to this brutality by practices like fustuarium. Cohorts that displayed acts of insubordination or cowardice were severely punished through fustuarium. In it, every tenth random soldier from a cohort was chosen and ordered to be stoned or clubbed to death by his fellow soldiers.

Leave a Comment