The Republican Roman Army

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  • The Army of Republican Rome

    The legions
    The fleet
    The allies

    It is hard to overestimate the importance of warfare in the Roman republic. Waging war was the most important way of acquiring the reputation and wealth that the Roman elite needed for a succesful political career. Each year new men came forward to fill the annually elected magistracies, each intent on securing their political future by achieving military victories that would ensure them the high honour of a triumphus. Rome was therefore in this period almost continually at war and gradually extending its power across Italy and the Mediterranean world.

    The legions

    Legionary armament
    The organisation
    The officers

    The Roman army of the middle republic was a militia army. It was composed of a number of legiones recruited among the citizen body which were levied for specific campaigns. Under normal circumstances four such legions were under arms which were assigned two apiece to the two consules. In case more units were needed these were placed under the command of praetores or pro-magistrates.

    The legiones were numbered sequentially with the numbers I to IV being reserved for the units under the command of the consules. Contrary to imperial practice the numbers carried by the units were not duplicated. The shifting of the composition of the army over the years meant that from time to time existing units received a new numeral. As units were levied for specific campaigns and disbanded when no longer needed, units did not have the opportunity to develop a distinct identity. The honorary titles so familiar of the imperial legions only developed during the first century BC as legions were kept under arms for a prolonged time.


    In republican Rome the right to serve in the army was a privilege of the assidui or propertied citizens. Together these formed the classis or populus. This restriction was imposed by the fact that the government generally did not take responsibility for the arming of its fighting men. Citizens were expected to equip themselves at their own cost with the necessary armour and weaponry when called up for service. Those not able to meet the property requirements for army service were known as the capite censi, the headcount, or as proletarii. These poorer citizens were only enrolled in times of emergency and equipped at state expense. Though the capite censi usually served as rowers in the navy they were at times incorporated in the legiones. Extreme measures were taken in the aftermath of Cannae with the formation of several units composed of volones, freed slave volunteers. Property qualifications for service in the army were gradually lowered as time went by to enlarge the potential pool of recruits. Generally the number of volunteers in the army was limited, though campaigns with lucrative prospects of plunder like those against Macedonia could attract larger quantities of men eager to serve.

    Roman citizens that met the property qualifications were liable for conscription from the age of seventeen, though repeated legislation against the enlistment of younger soldiers indicates that recruits could be very young indeed. Up to the age of 46 citizens of means remained under the obligation to serve. The maximum number of years to be spent in the army was set at sixteen, though this limit was removed in time of emergency. Gradually however it became the norm to serve six years in succession before being discharged with reservist obligations. Cavalrymen on the other hand had to serve ten campaigns before being released.

    The cavalry arm of the republican legion was constituted from wealthy citizens drawn mainly from the ordo equester able to meet the extra expense of providing a horse and its necessary equipment. Though a few select individuals served with a horse provided by the state, the socalled equus publicus, most cavalrymen bore the cost of their mounts themselves. The great financial burden of serving in the cavalry limited the size of the legionary horse. To some extent this lack of numbers was made up by the larger contingent of allied and auxiliary cavalry.

    Pay at this date was minimal, barely meeting the expenses for equipment, food and other necessities. Soldiers in the republican army therefore needed other sources of income. With Roman armies almost continually campaigning abroad the opportunity for plunder was however great. This helped ensure a continued support for expansion of the empire.

  • Glossary of Roman army terminology

  • Legionary armament

    The Roman cavalrymen were armed in a similar way to their counterparts in the Hellenistic armies. Legionary horsemen were equipped with helmet, body armour, shield, sword and a thrusting spear. The majority of troopers served as shock cavalry, though there are indications that some men may have served as ferentarii, light cavalry skirmishers. Legionary light infantrymen were at times intermixed with the cavalry to bolster its strength.

    The legionary infantry were divided in a number of classes with varying equipment and battlefield duties. The youngest and poorest soldiers served as light infantry which were known as velites, leves, rorarii or ferentarii. These light infantrymen were backed up by more heavily armed antesignani. The primary strength of the legio however resided in its heavy infantry. This was divided in three main divisions. The first of these were the hastati, the 'spearmen'. These consisted of relatively young soldiers and were usually deployed in the first battle line. The second class were the principes or 'leaders'. These men constituted the cream of the army and were normally deployed in the second battle line. The veteran triarii or pili made up the third class and were either deployed in the third battle line or left behind to guard the camp.

    The legionary light infantrymen were mostly equipped with a parma or buckler, a number of hastae velitariae or light javelins, a sword and a helmet covered with an animal pelt. Some may however been armed with a sling. The antesignani used to support the light troops carried equipment similar to the heavy infantry with pila and body armour being mentioned in the sources. The hastati, principes and triarii were equipped with helmet, body armour, greaves, swords and large scuta or shields. Most men wore a copper alloy pectorale, though the wealthiest legionaries wore either scale or mail armour or an anatomical cuirass. The men of the first two battle lines carried heavy javelins called pila, but the usual shaft weapon of the triarii was a long stabbing spear. Double edged swords were the main weapon used in combat, the famous gladius Hispaniensis being derived from Spanish examples. Torsion gun artillery was at times used by the legions in this period, though it may not have been allocated on a regular basis.

    The legion deployed usually in a formation of three battle lines of heavy infantry protected by a screen of skirmishers. The manipuli would initially deploy with the centuriae positioned one behind the other for ease of manoeuvre. Gaps were left between the manipuli but these were closed before engaging the enemy by the centuriae posteriores moving up to position themselves on the left of the centuriae priores. Tactics were generally simple consisting mainly of a blunt frontal attack. First the hastati would engage the enemy, throwing their pila before charging with their swords. These troops were relieved by the units of the principes in case of failure. The triarii were used as a last resort, the Latin expression ad triarios redisse being used to indicate that one was in a desperate position. Roman commanders confident in the ability of the hastati and principes to secure victory in battle left the triarii behind to guard the camp. Given the militia nature of the army at this point and the lack of prolonged and continuous training of the troops Roman tactics were by necessity predictable. Only when troops were kept under arms for years at a time could commanders like Scipio Africanus attempt to introduce more sophisticated tactics.

  • Glossary of Roman army terminology

  • The organisation

    The strength of a legio was variable and depended on the specific needs of a campaign. The authorised strength of foot varied between some 4200 to over 6000 infantrymen and the establishment strength of the horse varied between 200 and 300 troopers. In a legion of 4200 this was divided in some 1200 each of velites, hastati and principes and 600 triarii. An increase in the number of infantrymen did not affect the number of subunits as the strength of these was merely increased. It was also usual that when the legion's complement was strengthened the units of triarii generally received fewer extra men than the other classes of troops.

    A legio was subdivided in thirty manipuli consisting of two centuriae. Command of the manipulus lay in the hands of the senior centurio commanding the unit on the right of the formation, the officer of the other centuria acting as his deputy. The hastati, principes and triarii each had ten such manipuli numbered I to X. The other infantrymen were attached to these units having no separate organisation. The strength of the units of triarii was generally only half that of the hastati and principes Gradually new subdivisions called cohortes were introduced in the Roman legiones, probably patterned on similar formations of the Italic allies. In these units one manipulus of hastati, principes and triarii with their attached light infantrymen were brigaded together. The need for small independent units to fight against the tribesmen in the mountains of Spain is likely to have been the stimulus for the creation of these new legionary subdivisions.

    Each legio had its own organic cavalry arm. The usual strength of the legionary horse varied between 200 and 300 cavalrymen. These horsemen were organised in decuriae of each ten troopers under the command of a decurio, three decuriae being grouped together in a turma under the overall command of the senior decurio. Within each decuria a rearrank officer was appointed by its commander.

  • Glossary of Roman army terminology

  • The officers

    The command of a legio was entrusted to six tribuni militum drawn from the senatorial class. A minimum of five to ten years prior army service was required before men were eligible for the post of tribunus militum. Former praetores and consules as well as young men at the start of their public careers served as tribunus ensuring that at least part of these officers were experienced commanders. Part of the tribuni were elected by the popular assembly and known as comitiati while other officers of this rank termed Rufuli were selected by the commanders-in-chief. Junior officers known as centuriones were selected by the tribuni among the more experienced fighting men. Commanding the manipuli were the centurions called hastatus prior, princips prior and pilus prior with the hastatus posterior, princeps posterior and pilus posterior personally selected by the former acting as their deputies. Great prestige was attached to the post of primus pilus, the senior centurion commanding the first manipulus of triarii. As senior centurion of the legion this officer was admitted to the councils of the high command.

    The centuriones were assisted in their tasks by a small number of NCO's. The republican legionary organisation was however much simpler than the elaborate imperial system of principales and immunes. An optio served as a rearrank officer keeping the legionaries in check, a signifer carried the unit's standard and a tesserarius was in charge of the watchword. Attached to each manipulus as military musicians were further a cornicen and tubicen. Contrary to imperial practice the NCO's probably earned the same pay as the ordinary soldiers, centurions themselves at this time only being paid twice the amount of the rank and file.

  • Glossary of Roman army terminology

  • The fleet

    The military power of the Roman state had until the Punic Wars been mainly based on land. The struggle with Carthago forced the Romans however to become a maritime power as well. During the First Punic War a large fleet was built from scratch allegedly using a stranded Carthaginian vessel as a prototype. The standard type of warship was the quinqueremis with five rowers on three banks. The lack of skill of the Roman sailors meant that the traditional manner of naval combat with manoeuvring galleys trying to ram their opponents was abandoned for a new approach. Roman vessels were equipped with a corvus or raven, a movable boarding bridge which enabled the Romans to turn naval battles in engagements between marines rather than ships. This new invention enabled the Romans to score some spectacular successes against the Carthaginian fleet, but the added weight of the boarding bridge made their vessels less seaworthy resulting in heavy losses due to storms.

    The achievement of military superiority on sea during the Punic Wars enabled the Romans to land their land forces on the coast of North Africa to bring the war to their enemy. The naval supremacy gained by the Roman fleet also resulted in Carthago, formerly relying on its sea power, choosing to fight the Second Punic War on land instead. With the demise of Carthago as a leading naval threat the Romans lost interest in maintaining a powerful fleet themselves. With the seas no longer patrolled by warships this led to an increase in piracy in the Mediterranean.

  • Glossary of Roman army terminology

  • The allies

    The citizen troops serving in the legiones were supplemented by troops drawn from allied and conquered communities, the socii. Another term in general use for the socii was auxilia, supporting troops, or cohortes alariae. These forces were divided in several types but the most important were the Italic socii or allies. Among these the socii nominis Latinis, the allies of the Latin league, were the most prominent. Generally the majority of these Italic allies were staunchly loyal to the Roman cause. Even after the series of disastrous defeats inflicted by Hannibal only a minority of Italic communities defected to the enemy. The Italic socii were occasionally rewarded for their services by the granting of Latin rights or Roman citizenship. The increasing rarity of these grants in the second century BC was one of the main causes of the Social War fought between Rome and her Italic allies.

    The Italic allies were organised in alae sociorum, one of which was attached to each Roman legion. The name of ala or wing was derived from their usual position on the flanks of the citizen troops. As with the legions the establishment strength of these units was variable and adjusted to the requirements of the envisaged campaigns. Few allied communities were large enough to supply a full sized ala sociorum and therefore these units were usually composed of a number of contingents supplied by various allies. These contingents were organised in cohortes with a praetor drawn from the upper class in command. The allied praetores were however subordinated to Roman praefecti sociorum within the organisation of the alae.

    The exact structure of the allied alae is somewhat unclear. However most modern authorities assume that the units of the socii were generally similar in composition to the citizen troops with a mix of both light and heavy infantrymen and cavalrymen drawn from the same community. However some passages in the sources mention allied contingents consisting solely of skirmishers. This may indicate that there was no generalised pattern and the type as well as number of forces supplied varied for each ally. A major difference between the legions and the alae sociorum was in the number of horsemen attached. Generally the allied formations counted double or triple the number of cavalry attached to the citizen units.

    Among the Italic allies one fifth of the infantry and a third part of the horse were selected for service as pedites - and equites extraordinarii. This elite corps served as a bodyguard to the Roman generals and formed the vanguard on the march. These troops were organised in their own cohortes. If later imperial practice is a reliable guide, soldiers were individually picked for service in these guard formations. As a citizen counterpart to the allied extraordinarii some Roman commanders formed a cohors praetoria of picked legionary troops.

    In addition to the ground forces supplied by the Italic allies, the socalled socii navales, the naval allies, were responsible for furnishing Rome with ships and crews. After the Punic Wars Rome increasingly relied on such allies to supply the vessels and men whenever the formation of a fleet was required. The warships provided by the allies were of the current types such as triremes and quinqueremes.

    Next to the Italic allies existed other supplementary forces. Some of these were true allies bound by treaty obligations while others served as mercenaries. The numbers and type of these forces varied as much as their origin. Many were employed only in local campaigns, but Numidian light cavalry, Balearic slingers, Cretan archers, Gallic and Thracian horsemen regularly served in Roman armies far from their home countries. To some extent these troops provided complementary fighting skills to those of the Roman legions and their Italic allies.

  • Glossary of Roman army terminology

  • This page was made by Sander van Dorst

    Copyright by S. van Dorst 2000
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