Roman army

The Roman army (Latin: exercitus Romanus) was the terrestrial armed forces deployed by the Romans throughout the duration of Ancient Rome, from the Roman Kingdom (to c. 500 BC) to the Roman Republic (500–31 BC) and the Roman Empire (31 BC – 395), and its medieval continuation the Eastern Roman Empire. It is thus a term that may span approximately 2,206 years (753 BC to 1453 AD), during which the Roman armed forces underwent numerous permutations in composition, organisation, equipment and tactics, while conserving a core of lasting traditions.[1][2][3].

Solidus Julian-transparent
Coin showing (obverse) head of the late Roman emperor Julian (ruled 361–363 AD) wearing diadem and (reverse) soldier bearing standard holding kneeling barbarian captive by the hair, legend and Myth VIRTUS EXERCITUS ROMANORUM ("Valour of Roman army"). Gold solidus. Sirmium mint.

Historical overview

Early Roman army (c. 500 BC to c. 300 BC)

The Early Roman army was the armed force of the Roman Kingdom and of the early Republic (to c. 300 BC). During this period, when warfare chiefly consisted of small-scale plundering raids, it has been suggested that the army followed Etruscan or Greek models of organisation and equipment. The early Roman army was based on an annual levy.

The infantry ranks were filled with the lower classes while the cavalry (equites or celeres) were left to the patricians, because the wealthier could afford horses. Moreover, the commanding authority during the regal period was the high king. Until the establishment of the Republic and the office of consul, the king assumed the role of commander-in-chief.[4] However, from about 508 BC Rome no longer had a king. The commanding position of the army was given to the consuls, "who were charged both singly and jointly to take care to preserve the Republic from danger".[5]

The term legion is derived from the Latin word legio; which ultimately means draft or levy. At first there were only four legions. These legions were numbered "I" to "IIII", with the fourth being written as such and not "IV". The first legion was seen as the most prestigious. The bulk of the army was made up of citizens. These citizens could not choose the legion to which they were allocated. Any man "from ages 16–46 were selected by ballot" and assigned to a legion.[6]

Until the Roman military disaster of 390 BC at the Battle of the Allia, Rome's army was organised similarly to the Greek phalanx. This was due to Greek influence in Italy "by way of their colonies". Patricia Southern quotes ancient historians Livy and Dionysius in saying that the "phalanx consisted of 3,000 infantry and 300 cavalry".[7] Each man had to provide his equipment in battle; the military equipment which he could afford determined which position he took in the battle. Politically they shared the same ranking system in the Comitia Centuriata; which ultimately vis-à-vis placed the men on the battlefield.

Roman army of the mid-Republic (c. 300–88 BC)

The Roman army of the mid-Republic was also known as the "manipular army" or the "Polybian army" after the Greek historian Polybius, who provides the most detailed extant description of this phase. The Roman army started to have a full-time strength of 150,000 at all times and 3/4 of the rest were levied.

During this period, the Romans, while maintaining the levy system, adopted the Samnite manipular organisation for their legions and also bound all the other peninsular Italian states into a permanent military alliance (see Socii). The latter were required to supply (collectively) roughly the same number of troops to joint forces as the Romans to serve under Roman command. Legions in this phase were always accompanied on campaign by the same number of allied alae (Roman non-citizen auxiliaries), units of roughly the same size as legions.

After the 2nd Punic War (218–201 BC), the Romans acquired an overseas empire, which necessitated standing forces to fight lengthy wars of conquest and to garrison the newly gained provinces. Thus the army's character mutated from a temporary force based entirely on short-term conscription to a standing army in which the conscripts were supplemented by a large number of volunteers willing to serve for much longer than the legal six-year limit. These volunteers were mainly from the poorest social class, who did not have plots to tend at home and were attracted by the modest military pay and the prospect of a share of war booty. The minimum property requirement for service in the legions, which had been suspended during the 2nd Punic War, was effectively ignored from 201 BC onward in order to recruit sufficient volunteers. Between 150-100 BC, the manipular structure was gradually phased out, and the much larger cohort became the main tactical unit. In addition, from the 2nd Punic War onward, Roman armies were always accompanied by units of non-Italian mercenaries, such as Numidian light cavalry, Cretan archers, and Balearic slingers, who provided specialist functions that Roman armies had previously lacked.

Roman army of the late Republic (88–30 BC)

Roman Legionaries-MGR Lyon-IMG 1050
Imperial Roman legionaries in tight formation, a relief from Glanum, a Roman town in what is now southern France that was inhabited from 27 BC to 260 AD (when it was sacked by invading Alemanni)

The Roman army of the late Republic (88–30 BC) marks the continued transition between the conscription-based citizen-levy of the mid-Republic and the mainly volunteer, professional standing forces of the imperial era. The main literary sources for the army's organisation and tactics in this phase are the works of Julius Caesar, the most notable of a series of warlords who contested for power in this period. As a result of the Social War (91–88 BC), all Italians were granted Roman citizenship, the old allied alae were abolished and their members integrated into the legions. Regular annual conscription remained in force and continued to provide the core of legionary recruitment, but an ever-increasing proportion of recruits were volunteers, who signed up for 16-year terms as opposed to the maximum 6 years for conscripts. The loss of ala cavalry reduced Roman/Italian cavalry by 75%, and legions became dependent on allied native horse for cavalry cover. This period saw the large-scale expansion of native forces employed to complement the legions, made up of numeri ("units") recruited from tribes within Rome's overseas empire and neighbouring allied tribes. Large numbers of heavy infantry and cavalry were recruited in Spain, Gaul and Thrace, and archers in Thrace, Anatolia and Syria. However, these native units were not integrated with the legions, but retained their own traditional leadership, organisation, armour and weapons.

Imperial Roman army (30 BC – AD 284)

During this period the Republican system of citizen-conscription was replaced by a standing professional army of mainly volunteers serving standard 20-year terms (plus 5 as reservists), although many in the service of the empire would serve as many as 30 to 40 years on active duty, as established by the first Roman emperor, Augustus (sole ruler 30 BC – AD 14).Regular annual conscription of citizens was abandoned and only decreed in emergencies (e.g. during the Illyrian revolt 6–9 AD). Under Augustus there were 28 legions, consisting almost entirely of heavy infantry, with about 5,000 men each (total 125,000). This had increased to a peak of 33 legions of about 5,500 men each (c. 180,000 men in total) by AD 200 under Septimius Severus. Legions continued to recruit Roman citizens, mainly the inhabitants of Italy and Roman colonies, until 212. Legions were flanked by the auxilia, a corps of regular troops recruited mainly from peregrini, imperial subjects who did not hold Roman citizenship (the great majority of the empire's inhabitants until 212, when all were granted citizenship). Auxiliaries, who served a minimum term of 25 years, were also mainly volunteers, but regular conscription of peregrini was employed for most of the 1st century AD. The auxilia consisted, under Augustus, of about 250 regiments of roughly cohort size, that is, about 500 men (in total 125,000 men, or 50% of total army effectives). Under Severus the number of regiments increased to about 400, of which about 13% were double-strength (250,000 men, or 60% of total army). Auxilia contained heavy infantry equipped similarly to legionaries, and almost all the army's cavalry (both armoured and light), and archers and slingers.

Later Roman army (284–476 AD) continuing as East Roman army (476–641 AD)

0418 Befreiung einer belagerten Stadt Bodemuseum anagoria
Stone-carved relief depicting the liberation of a besieged city by a relief force, with those defending the walls making a sortie (i.e. a sudden attack against a besieging enemy from within the besieged town); Western Roman Empire, early 5th Century AD

The Late Roman army period stretches from (284–476 AD and its continuation, in the surviving eastern half of the empire, as the East Roman army to 641). In this phase, crystallised by the reforms of the emperor Diocletian (ruled 284–305 AD), the Roman army returned to regular annual conscription of citizens, while admitting large numbers of non-citizen barbarian volunteers. However, soldiers remained 25-year professionals and did not return to the short-term levies of the Republic. The old dual organisation of legions and auxilia was abandoned, with citizens and non-citizens now serving in the same units. The old legions were broken up into cohort or even smaller sizes. At the same time, a substantial proportion of the army's effectives were stationed in the interior of the empire, in the form of comitatus praesentales, armies that escorted the emperors.

Middle Byzantine army (641–1081 AD)

The Middle Byzantine army (641–1081 AD) was the army of the Byzantine state in its classical form (i.e. after the permanent loss of its Near Eastern and North African territories to the Arab conquests after 641 AD). This army was largely composed of semi-professional troops (soldier-farmers) based on the themata military provinces, supplemented by a small core of professional regiments known as the tagmata. Ibn al-Fakih estimated the strength of the themata forces in the East c. 902 at 85,000 and Kodama c. 930 at 70,000.[8] This structure pertained when the empire was on the defensive, in the 10th century the empire was increasingly involved in territorial expansion, and the themata troops became progressively more irrelevant, being gradually replaced by 'provincial tagmata' units and an increased use of mercenaries.

Komnenian Byzantine army (1081–1204)

The Komnenian Byzantine army was named after the Komnenos dynasty, which ruled from 1081–1185. This was an army built virtually from scratch after the permanent loss of half of Byzantium's traditional main recruiting ground of Anatolia to the Turks following the Battle of Manzikert in 1071, and the destruction of the last regiments of the old army in the wars against the Normans in the early 1080s. It survived until the fall of Constantinople to the Western crusaders in 1204. This army had a large number of mercenary regiments composed of troops of foreign origin such as the Varangian Guard, and the pronoia system was introduced.

Palaiologan Byzantine army (1261–1453)

The Palaiologan Byzantine army was named after the Palaiologos dynasty (1261–1453), which ruled Byzantium from the recovery of Constantinople from the Crusaders until its fall to the Turks in 1453. Initially, it continued some practices inherited from the Komnenian era and retained a strong native element until the late 13th century. During the last century of its existence, however, the empire was little more than a city-state that hired foreign mercenary bands for its defence. Thus the Byzantine army finally lost any meaningful connection with the standing imperial Roman army.

This article contains the summaries of the detailed linked articles on the historical phases above, Readers seeking discussion of the Roman army by theme, rather than by chronological phase, should consult the following articles:



Strategy and tactics

Equipment & other

Some of the Roman army's many tactics are still used in modern-day armies today.

Early Roman army (c. 550 to c. 300 BC)

Until c. 550 BC, there was no "national" Roman army, but a series of clan-based war-bands which only coalesced into a united force in periods of serious external threat. Around 550 BC, during the period conventionally known as the rule of king Servius Tullius, it appears that a universal levy of eligible adult male citizens was instituted. This development apparently coincided with the introduction of heavy armour for most of the infantry. Although originally low in numbers the Roman infantry was extremely tactical and developed some of the most influential battle strategies to date.

The early Roman army was based on a compulsory levy from adult male citizens which was held at the start of each campaigning season, in those years that war was declared. There were no standing or professional forces. During the Regal Era (to c. 500 BC), the standard levy was probably of 9,000 men, consisting of 6,000 heavily armed infantry (probably Greek-style hoplites), plus 2,400 light-armed infantry (rorarii, later called velites) and 600 light cavalry (equites celeres). When the kings were replaced by two annually elected praetores in c. 500 BC, the standard levy remained of the same size, but was now divided equally between the Praetors, each commanding one legion of 4,500 men.

It is likely that the hoplite element was deployed in a Greek-style phalanx formation in large set-piece battles. However, these were relatively rare, with most fighting consisting of small-scale border-raids and skirmishing. In these, the Romans would fight in their basic tactical unit, the centuria of 100 men. In addition, separate clan-based forces remained in existence until c. 450 BC at least, although they would operate under the Praetors' authority, at least nominally.

In 493 BC, shortly after the establishment of the Roman Republic, Rome concluded a perpetual treaty of military alliance (the foedus Cassianum), with the combined other Latin city-states. The treaty, probably motivated by the need for the Latins to deploy a united defence against incursions by neighbouring hill-tribes, provided for each party to provide an equal force for campaigns under unified command. It remained in force until 358 BC.

Roman army of the mid-Republic (c. 300 – 107 BC)

Altar Domitius Ahenobarbus Louvre n3bis
Levy of the army, detail of the carved relief on the Altar of Domitius Ahenobarbus, 122-115 BC.

The central feature of the Roman army of the mid-Republic, or the Polybian army, was the manipular organization of its battle-line. Instead of a single, large mass (the phalanx) as in the Early Roman army, the Romans now drew up in three lines consisting of small units (maniples) of 120 men, arrayed in chessboard fashion, giving much greater tactical strength and flexibility. This structure was probably introduced in c. 300 BC during the Samnite Wars. Also probably dating from this period was the regular accompaniment of each legion by a non-citizen formation of roughly equal size, the ala, recruited from Rome's Italian allies, or socii. The latter were c. 150 autonomous states which were bound by a treaty of perpetual military alliance with Rome. Their sole obligation was to supply to the Roman army, on demand, a number of fully equipped troops up to a specified maximum each year.

The Second Punic War (218–201 BC) saw the addition of a third element to the existing dual Roman/Italian structure: non-Italian mercenaries with specialist skills lacking in the legions and alae: Numidian light cavalry, Cretan archers, and slingers from the Balearic islands. From this time, these units always accompanied Roman armies.

The Republican army of this period, like its earlier forebear, did not maintain standing or professional military forces, but levied them, by compulsory conscription, as required for each campaigning season and disbanded thereafter (although formations could be kept in being over winter during major wars). The standard levy was doubled during the Samnite Wars to 4 legions (2 per Consul), for a total of c. 18,000 Roman troops and 4 allied alae of similar size. Service in the legions was limited to property-owning Roman citizens, normally those known as iuniores (age 16–46). The army's senior officers, including its commanders-in-chief, the Roman Consuls, were all elected annually at the People's Assembly. Only equites (members of the Roman knightly order) were eligible to serve as senior officers. Iuniores of the highest social classes (equites and the First Class of commoners) provided the legion's cavalry, the other classes the legionary infantry. The proletarii (those assessed at under 400 drachmae wealth) were ineligible for legionary service and were assigned to the fleets as oarsmen. Elders, vagrants, freedmen, slaves and convicts were excluded from the military levy, save in emergencies.

The legionary cavalry also changed, probably around 300 BC onwards from the light, unarmoured horse of the early army to a heavy force with metal armour (bronze cuirasses and, later, chain-mail shirts). Contrary to a long-held view, the cavalry of the mid-Republic was a highly effective force that generally prevailed against strong enemy cavalry forces (both Gallic and Greek) until it was decisively beaten by the Carthaginian general Hannibal's horsemen during the second Punic War. This was due to Hannibal's greater operational flexibility owing to his Numidian light cavalry.

The Polybian army's operations during its existence can be divided into three broad phases. (1) The struggle for hegemony over Italy, especially against the Samnite League (338–264 BC); (2) the struggle with Carthage for hegemony in the western Mediterranean Sea (264–201 BC); and (3) the struggle against the Hellenistic monarchies for control of the eastern Mediterranean (201–91 BC). During the earlier phase, the normal size of the levy (including allies) was in the region of 40,000 men (2 consular armies of c. 20,000 men each).

During the latter phase, with lengthy wars of conquest followed by permanent military occupation of overseas provinces, the character of the army necessarily changed from a temporary force based entirely on short-term conscription to a standing army in which the conscripts, whose service was in this period limited by law to 6 consecutive years, were complemented by large numbers of volunteers who were willing to serve for much longer periods. Many of the volunteers were drawn from the poorest social class, which until the 2nd Punic War had been excluded from service in the legions by the minimum property requirement: during that war, extreme manpower needs had forced the army to ignore the requirement, and this practice continued thereafter. Maniples were gradually phased out as the main tactical unit, and replaced by the larger cohorts used in the allied alae, a process probably complete by the time the general Marius assumed command in 107 BC. (The "Marian reforms" of the army hypothesised by some scholars are today seen by other scholars as having evolved earlier and more gradually.)

In the period after the defeat of Carthage in 201 BC, the army was campaigning exclusively outside Italy, resulting in its men being away from their home plots of land for many years at a stretch. They were assuaged by the large amounts of booty that they shared after victories in the rich eastern theatre. But in Italy, the ever-increasing concentration of public lands in the hands of big landowners, and the consequent displacement of the soldiers' families, led to great unrest and demands for land redistribution. This was successfully achieved, but resulted in the disaffection of Rome's Italian allies, who as non-citizens were excluded from the redistribution. This led to the mass revolt of the socii and the Social War (91-88 BC). The result was the grant of Roman citizenship to all Italians and the end of the Polybian army's dual structure: the alae were abolished and the socii recruited into the legions.

Imperial Roman army (30 BC – AD 284 )

God Bes as a Roman soldier. Sword in right hand and spear and shield in left hand. Limestone slab, in relief. Roman Period. From Egypt. The Petrie Museum of Egyptian Archaeology, London
God Bes as a Roman soldier. Sword in right hand and spear and shield in left hand. Limestone slab, in relief. Roman Period. From Egypt. The Petrie Museum of Egyptian Archaeology, London
Roman military clothes National Military Museum Bucharest Romania
Recreation of a Roman soldier wearing plate armour (lorica segmentata), National Military Museum, Romania.
Lens - Inauguration du Louvre-Lens le 4 décembre 2012, la Galerie du Temps, n° 058
Roman relief fragment depicting the Praetorian Guard, c. 50 AD
1636 - Archaeological Museum, Athens - Roman statue of a man - Photo by Giovanni Dall'Orto, Nov 11 2009
Ancient Roman statue fragment of either a general or an emperor wearing a corselet decorated with Selene, and two Nereids. Found at èmegara, dating from 100-130 AD.
Column of Marcus Aurelius - detail1
Relief scene of Roman legionaries marching, from the Column of Marcus Aurelius, Rome, Italy, 2nd century AD

Under the founder–emperor Augustus (ruled 30 BC – 14 AD), the legions, c. 5,000-strong all-heavy infantry formations recruited from Roman citizens only, were transformed from a mixed conscript and volunteer corps serving an average of 10 years, to all-volunteer units of long-term professionals serving a standard 25-year term (conscription was only decreed in emergencies). In the later 1st century, the size of a legion's First Cohort was doubled, increasing legionary personnel to c. 5,500.

Alongside the legions, Augustus established the auxilia, a regular corps of similar numbers to the legions, recruited from the peregrini (non-citizen inhabitants of the empire – about 90% of the empire's population in the 1st century). As well as comprising large numbers of extra heavy infantry equipped in a similar manner to legionaries, the auxilia provided virtually all the army's cavalry (heavy and light), light infantry, archers and other specialists. The auxilia were organised in c. 500-strong units called cohortes (all-infantry), alae (all-cavalry) and cohortes equitatae (infantry with a cavalry contingent attached). Around 80 AD, a minority of auxiliary regiments were doubled in size. Until about 68 AD, the auxilia were recruited by a mix of conscription and voluntary enlistment. After that time, the auxilia became largely a volunteer corps, with conscription resorted to only in emergencies. Auxiliaries were required to serve a minimum of 25 years, although many served for longer periods. On completion of their minimum term, auxiliaries were awarded Roman citizenship, which carried important legal, fiscal and social advantages. Alongside the regular forces, the army of the Principate employed allied native units (called numeri) from outside the empire on a mercenary basis. These were led by their own aristocrats and equipped in traditional fashion. Numbers fluctuated according to circumstances and are largely unknown.

As all-citizen formations, and symbolic garantors of the dominance of the Italian "master-nation", legions enjoyed greater social prestige than the auxilia. This was reflected in better pay and benefits. In addition, legionaries were equipped with more expensive and protective armour than auxiliaries. However, in 212, the emperor Caracalla granted Roman citizenship to all the empire's inhabitants. At this point, the distinction between legions and auxilia became moot, the latter becoming all-citizen units also. The change was reflected in the disappearance, during the 3rd century, of legionaries' special equipment, and the progressive break-up of legions into cohort-sized units like the auxilia.

By the end of Augustus' reign, the imperial army numbered some 250,000 men, equally split between legionaries and auxiliaries (25 legions and c. 250 auxiliary regiments). The numbers grew to a peak of about 450,000 by 211 (33 legions and c. 400 auxiliary regiments). By then, auxiliaries outnumbered legionaries substantially. From the peak, numbers probably underwent a steep decline by 270 due to plague and losses during multiple major barbarian invasions. Numbers were restored to their early 2nd-century level of c. 400,000 (but probably not to their 211 peak) under Diocletian (r. 284–305). After the empire's borders became settled (on the Rhine-Danube line in Europe) by 68, virtually all military units (except the Praetorian Guard) were stationed on or near the borders, in roughly 17 of the 42 provinces of the empire in the reign of Hadrian (r. 117–38).

The military chain of command was relatively uniform across the Empire. In each province, the deployed legions' legati (legion commanders, who also controlled the auxiliary regiments attached to their legion) reported to the legatus Augusti pro praetore (provincial governor), who also headed the civil administration. The governor in turn reported direct to the emperor in Rome. There was no army general staff in Rome, but the leading praefectus praetorio (commander of the Praetorian Guard) often acted as the emperor's de facto military chief-of-staff.

Legionary rankers were relatively well-paid, compared to contemporary common labourers. Compared with their subsistence-level peasant families, they enjoyed considerable disposable income, enhanced by periodic cash bonuses on special occasions such as the accession of a new emperor. In addition, on completion of their term of service, they were given a generous discharge bonus equivalent to 13 years' salary. Auxiliaries were paid much less in the early 1st century, but by 100 AD, the differential had virtually disappeared. Similarly, in the earlier period, auxiliaries appear not to have received cash and discharge bonuses, but probably did so from Hadrian onwards. Junior officers (principales), the equivalent of non-commissioned officers in modern armies, could expect to earn up to twice basic pay. Legionary centurions, the equivalent of mid-level commissioned officers, were organised in an elaborate hierarchy. Usually risen from the ranks, they commanded the legion's tactical sub-units of centuriae (c. 80 men) and cohorts (c. 480 men). They were paid several multiples of basic pay. The most senior centurion, the primus pilus, was elevated to equestrian rank upon completion of his single-year term of office. The senior officers of the army, the legati legionis (legion commanders), tribuni militum (legion staff officers) and the praefecti (commanders of auxiliary regiments) were all of at least equestrian rank. In the 1st and early 2nd centuries, they were mainly Italian aristocrats performing the military component of their cursus honorum (conventional career-path). Later, provincial career officers became predominant. Senior officers were paid enormous salaries, multiples of at least 50 times basic.

A typical Roman army during this period consisted of five to six legions. One legion was made up of 10 cohorts. The first cohort had five centuria each of 160 soldiers. In the second through tenth cohorts there were six centuria of 80 men each. These do not include archers, cavalry or officers.

Soldiers spent only a fraction of their lives on campaign. Most of their time was spent on routine military duties such as training, patrolling, and maintenance of equipment etc. Soldiers also played an important role outside the military sphere. They performed the function of a provincial governor's police force. As a large, disciplined and skilled force of fit men, they played a crucial role in the construction of a province's Roman military and civil infrastructure: in addition to constructing forts and fortified defences such as Hadrian's Wall, they built roads, bridges, ports, public buildings, entire new cities (Roman colonies), and also engaged in large-scale forest clearance and marsh drainage to expand the province's available arable land.

Soldiers, mostly drawn from polytheistic societies, enjoyed wide freedom of worship in the polytheistic Roman system. They revered their own native deities, Roman deities and the local deities of the provinces in which they served. Only a few religions were banned by the Roman authorities, as being incompatible with the official Roman religion and/or politically subversive, notably Druidism and Christianity. The later Principate saw the rise in popularity among the military of Eastern mystery cults, generally centred on one deity, and involving secret rituals divulged only to initiates. By far the most popular in the army was Mithraism, an apparently syncretist religion which mainly originated in Asia Minor.

Late Roman army/East Roman army (284–641)

The Late Roman army is the term used to denote the military forces of the Roman Empire from the accession of Emperor Diocletian in 284 until the Empire's definitive division into Eastern and Western halves in 395. A few decades afterwards, the Western army disintegrated as the Western empire collapsed. The East Roman army, on the other hand, continued intact and essentially unchanged until its reorganization by themes and transformation into the Byzantine army in the 7th century. The term "late Roman army" is often used to include the East Roman army.

The army of the Principate underwent a significant transformation, as a result of the chaotic 3rd century. Unlike the Principate army, the army of the 4th century was heavily dependent on conscription and its soldiers were more poorly remunerated than in the 2nd century. Barbarians from outside the empire probably supplied a much larger proportion of the late army's recruits than in the army of the 1st and 2nd centuries.

The size of the 4th-century army is controversial. More dated scholars (e.g. A.H.M. Jones, writing in the 1960s) estimated the late army as much larger than the Principate army, half the size again or even as much as twice the size. With the benefit of archaeological discoveries of recent decades, many contemporary historians view the late army as no larger than its predecessor: under Diocletian c. 390,000 (the same as under Hadrian almost two centuries earlier) and under Constantine no greater, and probably somewhat smaller, than the Principate peak of c. 440,000. The main change in structure was the establishment of large armies that accompanied the emperors (comitatus praesentales) and were generally based away from the frontiers. Their primary function was to deter usurpations. The legions were split up into smaller units comparable in size to the auxiliary regiments of the Principate. In parallel, legionary armour and equipment were abandoned in favour of auxiliary equipment. Infantry adopted the more protective equipment of the Principate cavalry.

The role of cavalry in the late army does not appear to have been enhanced as compared with the army of the Principate. The evidence is that cavalry was much the same proportion of overall army numbers as in the 2nd century and that its tactical role and prestige remained similar. Indeed, the cavalry acquired a reputation for incompetence and cowardice for their role in three major battles in mid-4th century. In contrast, the infantry retained its traditional reputation for excellence.

The 3rd and 4th centuries saw the upgrading of many existing border forts to make them more defensible, as well as the construction of new forts with much higher defensive specifications. The interpretation of this trend has fuelled an ongoing debate whether the army adopted a defence-in-depth strategy or continued the same posture of "forward defence" as in the early Principate. Many elements of the late army's defence posture were similar to those associated with forward defence, such as a looser forward location of forts, frequent cross-border operations, and external buffer-zones of allied barbarian tribes. Whatever the defence strategy, it was apparently less successful in preventing barbarian incursions than in the 1st and 2nd centuries. This may have been due to heavier barbarian pressure, and/or to the practice of keeping large armies of the best troops in the interior, depriving the border forces of sufficient support.

Komnenian Byzantine army (1081–1204)

Jean II Comnene
Emperor John II Komnenos, the most successful commander of the Komnenian army.

The Komnenian period marked a rebirth of the Byzantine army. At the beginning of the Komnenian period in 1081, the Byzantine Empire had been reduced to the smallest territorial extent. Surrounded by enemies, and financially ruined by a long period of civil war, the empire's prospects looked grim.

At the beginning of the Komnenian period, the Byzantine army was reduced to a shadow of its former self: during the 11th century, decades of peace and neglect had reduced the old thematic forces, and the Battle of Manzikert in 1071 had destroyed the professional tagmata, the core of the Byzantine army. At Manzikert and later at Dyrrhachium, units tracing their lineage for centuries back to Late Roman army were wiped out, and the subsequent loss of Asia Minor deprived the Empire of its main recruiting ground. In the Balkans, at the same time, the Empire was exposed to invasions by the Norman Kingdom of Sicily, and by Pecheneg raids across the Danube.

The Byzantine army's nadir was reached in 1091, when Alexios I could manage to field only 500 soldiers from the Empire's professional forces. These formed the nucleus of the army, with the addition of the armed retainers of Alexios' relatives and the nobles enrolled in the army and the substantial aid of a large force of allied Cumans, which won the Battle of Levounion against the Pechenegs (Petcheneks or Patzinaks).[9] Yet, through a combination of skill, determination and years of campaigning, Alexios, John and Manuel Komnenos managed to restore the power of the Byzantine Empire by constructing a new army from scratch. This process should not, however, at least in its earlier phases, be seen as a planned exercise in military restructuring. In particular, Alexios I was often reduced to reacting to events rather than controlling them; the changes he made to the Byzantine army were largely done out of immediate necessity and were pragmatic in nature.

The new force had a core of units which were both professional and disciplined. It contained formidable guards units such as the Varangians, the Athanatoi, a unit of heavy cavalry stationed in Constantinople, the Vardariotai and the Archontopouloi, recruited by Alexios from the sons of dead Byzantine officers, foreign mercenary regiments, and also units of professional soldiers recruited from the provinces. These provincial troops included kataphraktoi cavalry from Macedonia, Thessaly and Thrace, and various other provincial forces such as Trebizond Archers from the Black Sea coast of Anatolia. Alongside troops raised and paid for directly by the state the Komnenian army included the armed followers of members of the wider imperial family and its extensive connections. In this can be seen the beginnings of the feudalisation of the Byzantine military. The granting of pronoia holdings, where land, or more accurately rights to revenue from land, was held in return for military obligations, was beginning to become a notable element in the military infrastructure towards the end of the Komnenian period, though it became much more important subsequently.

In 1097, the Byzantine army numbered around 70,000 men altogether.[10] By 1180 and the death of Manuel Komnenos, whose frequent campaigns had been on a grand scale, the army was probably considerably larger. During the reign of Alexios I, the field army numbered around 20,000 men which was increased to about 30,000 men in John II's reign.[11] By the end of Manuel I's reign the Byzantine field army had risen to 40,000 men.

Palaiologan Byzantine army (1261–1453)

The Palaiologan army refers to the military forces of the Byzantine Empire from the late 13th century to its final collapse in the mid 15th century, under the House of the Palaiologoi. The army was a direct continuation of the forces of the Nicaean army, which itself was a fractured component of the formidable Komnenian army. Under the first Palaiologan emperor, Michael VIII, the army's role took an increasingly offensive role whilst the naval forces of the Empire, weakened since the days of Andronikos I Komnenos, were boosted to include thousands of skilled sailors and some 80 ships. Due to the lack of land to support the army, the Empire required the use of large numbers of mercenaries.

After Andronikos II took to the throne, the army fell apart and the Byzantines suffered regular defeats at the hands of their eastern opponents, although they would continue to enjoy success against the crusader territories in Greece. By c. 1350, following a destructive civil war and the outbreak of the Black Death, the Empire was no longer capable of raising troops and the supplies to maintain them. The Empire came to rely upon troops provided by Serbs, Bulgarians, Venetians, Latins, Genoans and Ottoman Turks to fight the civil wars that lasted for the greater part of the 14th century, with the latter foe being the most successful in establishing a foothold in Thrace. The Ottomans swiftly expanded through the Balkans and cut off Constantinople, the capital of the Byzantine Empire, from the surrounding land. The last decisive battle was fought by the Palaiologan army in 1453, when Constantinople was besieged and fell on 29 May. The last isolated remnants of the Byzantine state were conquered by 1461.

See also


  1. ^ The Complete Roman Army, Adrian Goldsworthy Thames & Hudson, 2011
  2. ^ The Roman Army: A Social and Institutional History, Pat Southern, Oxford University Press, 2007
  3. ^ Companion to the Roman Army, Paul Erdkamp, John Wiley & Sons, 31 Mar 2011
  4. ^ Rostovtzeff, Michael. Rome. Oxford, England: Oxford University Press, 1960
  5. ^ Vegetius, The Military Institutions of the Romans (J. Clark, transl.) Harrisburg Penn.; 1944.
  6. ^ Dando-Collins, Stephen. Legions of Rome. New York: St. Martin's Press, 2010.
  7. ^ Southern, Pat. The Roman Army: A Social and Institutional History. Oxford, England: Oxford University Press, 2007.
  8. ^ Heath, Ian (1979). Byzantine armies, 886-1118. Osprey. p. 19. ISBN 978-0850453065.
  9. ^ Angold, p. 127
  10. ^ Konstam, p. 141.
  11. ^ W. Treadgold, A History of the Byzantine State and Society, 680

External links

Battle of Zama

The Battle of Zama—fought in 202 BC near Zama (Tunisia)—marked the end of the Second Punic War. A Roman army led by Publius Cornelius Scipio Africanus (Scipio), with crucial support from Numidian leader Masinissa, defeated the Carthaginian army led by Hannibal.

After defeating Carthaginian and Numidian armies at the battles of Utica and the Great Plains, Scipio imposed peace terms on the Carthaginians, who had no choice but to accept them. At the same time they recalled their general Hannibal's army from Italy. Confident in Hannibal's forces, the Carthaginians broke the armistice with Rome. Scipio and Hannibal confronted each other near Zama Regia. Hannibal had 36,000 infantry to Scipio's 29,000. One-third of Hannibal's army were citizen levies and the Romans had 6,100 cavalry to Carthage's 4,000, as most of the Numidian cavalry that Hannibal had employed with great success in Italy had defected to the Romans.

Hannibal also employed 80 war elephants. The elephants opened the battle by charging the main Roman army. Scipio's soldiers avoided the elephants by opening their ranks and drove them off with missiles. The Roman and Numidian cavalry subsequently defeated the Carthaginian cavalry and chased them from the battlefield. Hannibal's first line of mercenaries attacked Scipio's infantry and were defeated. The second line of citizen levies and the mercenaries' remnants assaulted and inflicted heavy losses on the Roman first line. The Roman second line joined the struggle and pushed back the Carthaginian assault. Hannibal's third line of veterans, reinforced by the citizen levies and mercenaries, faced off against the Roman army, which had been redeployed into a single line. The combat was fierce and evenly matched. Finally, Scipio's cavalry returned to the battle and attacked Hannibal's army in the rear, routing and destroying it.

The Carthaginians lost 20,000–25,000 killed and 8,500–20,000 captured. Scipio lost 4,000–5,000 men, 1,500–2,500 Romans and 2,500 Numidians, killed. Defeated on their home ground, the Carthaginian ruling elite sued for peace and accepted humiliating terms, ending the 17-year war.


In the Roman Republic and the Roman Empire, the Latin word castrum (plural castra) was a building, or plot of land, used as a fortified military camp.

Castrum was the term used for different sizes of camps including a large legionary fortress, smaller auxiliary forts, temporary encampments, and "marching" forts. The diminutive form castellum was used for fortlets, typically occupied by a detachment of a cohort or a century.

In English, the terms Roman fortress, Roman fort, and Roman camp are commonly used for castrum. However, scholastic convention tends toward the use of the words camp, marching camp, and fortress as a translation of castrum.For a list of known castra see List of castra.


A centurion (; Latin: centurio; Greek: κεντυρίων, kentyríōn or ἑκατόνταρχος, hekatóntarkhos) was a professional officer of the Roman army after the Marian reforms of 107 BC. Most centurions commanded groups of centuries of around 100 legionaries, but senior centurions commanded cohorts or took senior staff roles in their legion. Centurions were also found in the Roman navy. In the Byzantine Army, they were also known by the name kentarch (κένταρχος, kentarchos). Their symbol of office was the vine staff, with which they disciplined even Roman citizens protected from other forms of beating by the Porcian Laws.

Decimation (Roman army)

Decimation (Latin: decimatio; decem = "ten") was a form of military discipline used by senior commanders in the Roman Army to punish units or large groups guilty of capital offences, such as cowardice, mutiny, desertion, and insubordination, and for pacification of rebellious legions. The word decimation is derived from Latin meaning "removal of a tenth".

The procedure was a pragmatic attempt to balance the need to punish serious offences with the realities of managing a large group of offenders.

East Roman army

The East Roman army refers to the army of the Eastern section of the Roman Empire, from the empire's definitive split in 395 AD to the army's reorganization by themes after the permanent loss of Syria, Palestine and Egypt to the Arabs in the 7th century during the Byzantine-Arab Wars. The East Roman army is the continuation of the Late Roman army of the 4th century until the Byzantine army of the 7th century onwards.

The East Roman army was a direct continuation of the eastern portion of the late Roman army, from before the division of the empire. The east Roman army started with the same basic organization as the late Roman army and its West Roman counterpart, but between the 5th and 7th centuries, the cavalry grew more important, the field armies took on more tasks, and the border armies were transformed into local militias.

In the 6th century, the emperor Justinian I, who reigned from 527 to 565, sent much of the East Roman army to try to reconquer the former Western Roman Empire. In these wars, the East Roman empire reconquered parts of North Africa from the Vandal kingdom and Italy from the Ostrogothic Kingdom, as well as parts of southern Spain. The power of the army diminished in his reign owing to bubonic plague .In the 7th century, the emperor Heraclius led the east Roman army against the Sasanian Empire, temporarily regaining Egypt and Syria, and then against the Rashidun Caliphate. His defeat at the Battle of Yarmuk would lead to the Islamic conquest of Syria and Egypt, and would force the reorganization of the East Roman army, leading to the thematic system of later Byzantine armies.

Late Roman army

In modern scholarship, the "late" period of the Roman army begins with the accession of the Emperor Diocletian in AD 284, and ends in 476 with the deposition of Romulus Augustulus, being roughly coterminous with the Dominate. During the period 395–476, the army of the Roman Empire's western half progressively disintegrated, while its counterpart in the East, known as the East Roman army (or the early Byzantine army) remained largely intact in size and structure until the reign of Justinian I (r. AD 527–565).The Imperial Roman army of the Principate (30 BC – 284 AD) underwent a significant transformation as a result of the chaotic 3rd century. Unlike the army of the Principate, the army of the 4th century was heavily dependent on conscription and its soldiers were paid much less than in the 2nd century. Barbarians from outside the empire probably supplied a much larger proportion of the late army's recruits than in the army of the 1st and 2nd centuries, but there is little evidence that this adversely affected the army's performance.

Scholarly estimates of the size of the 4th-century army diverge widely, ranging from ca. 400,000 to over one million effectives (i.e. from roughly the same size as the 2nd-century army to 2 or 3 times larger). This is due to fragmentary evidence, unlike the much better-documented 2nd-century army.

Under the Tetrarchy, military commands were separated from administrative governorships for the first time, in contrast to the Principate, where provincial governors were also commanders-in-chief of all military forces deployed in their provinces.

The main change in structure from the 2nd-century army was the establishment of large escort armies (comitatus praesentales), typically containing 20,000–30,000 top-grade palatini troops. These were normally based near the imperial capitals: (Constantinople in the East, Milan in the West), thus far from the empire's borders. These armies' primary function was to deter usurpers, and they usually campaigned under the personal command of their emperors. The legions were split into smaller units comparable in size to the auxiliary regiments of the Principate. Infantry adopted the more protective equipment of the Principate cavalry.

The role of cavalry in the late army does not appear to have been greatly enhanced as compared with the army of the Principate. The evidence is that cavalry was much the same proportion of overall army numbers as in the 2nd century and that its tactical role and prestige remained similar. However, the cavalry of the Late Roman army was endowed with greater numbers of specialised units, such as extra-heavy shock cavalry (cataphractii and clibanarii) and mounted archers. During the later 4th century, the cavalry acquired a reputation for incompetence and cowardice for their role in three major battles. In contrast, the infantry retained its traditional reputation for excellence.

The 3rd and 4th centuries saw the upgrading of many existing border forts to make them more defensible, as well as the construction of new forts with stronger defenses. The interpretation of this trend has fuelled an ongoing debate whether the army adopted a defence-in-depth strategy or continued the same posture of "forward defence" as in the early Principate. Many elements of the late army's defence posture were similar to those associated with forward defence, such as forward location of forts, frequent cross-border operations, and external buffer-zones of allied barbarian tribes. Whatever the defence strategy, it was apparently less successful in preventing barbarian incursions than in the 1st and 2nd centuries. This may have been due to heavier barbarian pressure, or to the practice of keeping large armies of the best troops in the interior, depriving the border forces of sufficient support.


A legatus (anglicized as legate) was a high-ranking Roman military officer in the Roman Army, equivalent to a modern high-ranking general officer. Initially used to delegate power, the term became formalized under Augustus as the officer in command of a legion.

From the times of the Roman Republic, legates received large shares of the military's rewards at the end of a successful campaign. This made the position a lucrative one, so it could often attract even distinguished consuls or other high-ranking political figures within Roman politics (e.g., the consul Lucius Julius Caesar volunteered late in the Gallic Wars as a legate under his first cousin once removed, Gaius Julius Caesar).

List of Roman army unit types

This is a list of Roman army unit types.

Actarius – A military or camp clerk.

Adiutor – A camp or headquarters adjutant or assistant

Aeneator – Military musician such as a bugler.

Agrimensor – A surveyor (a type of immunes).

Aquilifer – Bearer of the legionary eagle.

Alaris – A cavalryman serving in an ala.

Architecti – An engineer or artillery constructor.

Armicustos – A soldier tasked with the administration and supply of weapons and equipment. A quartermaster.

Ballistarius – An artillery operator (a type of immunes).

Beneficiarius – A soldier performing an extraordinary task such as military policing or a special assignment.

Bucinator – A trumpeter or bugler.

Cacula – Servant or slave of a soldier.

Capsarior – A medical orderly.

Causarius – A soldier discharged for wounds or other medical reasons.

Centurion – Officer rank, generally one per 80 soldiers, in charge of a centuria.

Clinicus – A medic.

Cornicen – Bugler.

Doctor – A trainer, subdivisions for everything from weapons to hornblowing.

Draconarius – Bearer of a cavalry standard.

Decurion – Leader of a troop of cavalry (14-30 men). Often confused with decanus.

Decanus – Leader of a contubernium (a legionary tent group of 8 men).

Discens – Miles in training for an immunis position.

Dux – A general in charge of two or more legions. In the Third Century AD, an officer with a regional command transcending provincial boundaries, responsible directly to the emperor alone, usually appointed on a temporary basis in a grave emergency. In the fourth century AD, an officer in charge of a section of the frontier answering to the Magister Militum.

Equites singulares Augusti – Elite cavalry unit tasked to guard the Roman Emperors. Usually commanded by a tribunus of praetorian rank.

Evocatus – A soldier who had served out his time and obtained his discharge (missio), but had voluntarily enlisted again at the invitation of the consul or other commander.

Frumentarii – Officials of the Roman Empire during the 2nd and 3rd era. Often used as a Secret Service, mostly operating in uniform.

Hastatus – The youngest of the heavy infantry in the pre-Marian armies, who were less well-equipped than the older Principes and Triarii. These formed the first line of battle in front of the Principes.

Hastatus Prior – A centurion commanding a manipulus or centuria of hastati. A high-ranking officer within a manipulus or centuria.

Hastatus Posterior – A deputy to the hastatus prior

Hastiliarius – a weapons instructor.

Imaginifer – A standard-bearer carrying the imago – the standard which bore a likeness of the emperor, and, at later dates, his family.

Immunes – Soldiers who were "immune" from combat duty and fatigues through having a more specialist role within the army.

Legatus legionis – A legion commander of senatorial rank; literally the "deputy" of the emperor, who was the titular commander-in-chief.

Legatus pro praetore – Provincial governor of senatorial rank with multiple legions under his command.

Legionary – The heavy infantry that was the basic military force of the ancient Roman army in the period of the late Roman Republic and the Roman Empire.

Medicus – Physician or combat medic. Specializations included surgery (medicus vulnerarius), ophthalmology (medicus ocularius), and also veterinary (medicus veterinarius). At least some held rank equivalent to a centurion.

Miles or Miles Gregarius – The basic private level foot soldier.

Numerus – A unit of barbarian allies not integrated into the regular army structure. Later, a unit of border forces.

Optio – One per century as second-in-command to the centurion. Could also fill several other specialized roles on an ad hoc basis.

Pedites – The infantry of the early army of the Roman kingdom. The majority of the army in this period.

Peditatus – A term referring to any infantryman in the Roman Empire.

Pilus Prior – Senior centurion of a cohort.

Pilus Posterior – Deputy to the pilus prior.

Praefectus Castrorum – Camp prefect, third-in-command of the legion, also responsible for maintaining the camp, equipment, and supplies. Usually a former primus pilus.

Praefectus Cohortis - Commander of a cohort.

Praefectus legionis agens vice legati – Equestrian officer given the command of a legion in the absence of a senatorial legatus. After the removal of senators from military command, the title of a legionary commander. ("...agens vice legati, dropped in later Third Century")

Praetorians – A special force of bodyguards used by Roman Emperors.

Primus Ordinis – The commanding officer of each centuria in the first cohort with the exception of the first centuria of the cohort.

Primus Pilus (literally 'first file', not spear) – The centurion commanding the first cohort and the senior centurion of the entire Legion.

Princeps – Pre-Marian soldier, initially equipped with the Hasta spear, but later with the pilum, these men formed the second line of battle behind the Hastati in the pre-Marian armies. They were also chieftains in Briton like Dumnorix of the Regneses (he was killed by Gaius Salvius Liberalis' soldiers).

Princeps Prior – A centurion commanding a century of principes.

Princeps Posterior – A deputy to the princeps prior.

Principales – A group of ranks, including aquilifer, signifer, optio, and tesserarius. Similar to modern NCOs (Non-commissioned officers).

Protectores Augusti Nostri (a.k.a. Protectores Divini Lateris) – honorific title for senior officers singled out for their loyalty to the Emperor and soldierly qualities. The protectores were an order of honor rather than a military unit. The order first appeared in the mid-200s AD.

Quaestionarius – An interrogator or torturer.

Retentus – A soldier kept in service after serving required term.

Rorarii – The final line, or reserve, in the ancient pre-Marius Roman army. These were removed even before the Marian reforms, as the Triarii provided a very sturdy anchor.

Sagittarii – Archers, including horse-riding auxiliary archers recruited mainly in the Eastern Empire and Africa.

Salararius – A soldier enjoying special service conditions or hired as a mercenary.

Scholae Palatinae – An elite troop of soldiers created by the Emperor Constantine the Great to provide personal protection of the Emperor and his immediate family.

Scorpionarius – An artilleryman operating a scorpio artillery piece.

Signifer – Standard bearer of the Roman Legion.

Socii – Troops from allied states in the pre-Marian army before the Social War (91–88 BC)

Speculatores and Exploratores – The scouts and reconnaissance element of the Roman army.

Supernumerarii – Supernumerary soldiers who served to fill the places of those who were killed or disabled by their wounds.

Tablifer – A guard cavalry standard-bearer

Tesserarius – Guard commander, one per centuria.

Tirones – A basic trainee.

Triarii – Spearmen of the pre-Marian armies, equipped with the Hasta, who formed the third line of battle behind the Principes.

Tribuni militum angusticlavii or military tribune – Military tribune of equestrian rank, five of whom were assigned to each legion.

Tribunus militum laticlavius – Military tribune of senatorial rank. Second in command of a legion. Appointments to this rank seem to have ceased during the sole reign of Gallienus as part of a policy of excluding senators from military commands.

Tubicen – A trumpeter.

Urbanae – A special police force of Rome, created to counterbalance the Praetorians.

Velites – A class of light infantry in the army of the Roman Republic.

Venator – A hunter (a type of immunes).

Vexillarius – Bearer of a vexillum (standard).

List of Roman wars and battles

The following is a List of Roman wars and battles fought by the ancient Roman Kingdom, Roman Republic and Roman Empire, organized by date.

Magnae Carvetiorum

Magnae, fully Magnae Carvetiorum (Latin for "The Greats of the Carvetii"), was a Roman fort on Hadrian's Wall in northern Britain. Its ruins are now known as Carvoran Roman Fort and are located near Carvoran, Northumberland, in northern England. It is thought to have been sited with reference to the Stanegate Roman road, before the building of Hadrian's Wall, to which it is not physically attached. In fact the Vallum ditch unusually goes north of the fort, separating it from the Wall.

The fort is now the site of the Roman Army Museum.

Military history of ancient Rome

The military history of ancient Rome is inseparable from its political system, based from an early date upon competition within the ruling elite. Two consuls were elected each year to head the government of the state, and in the early to mid-Republic were assigned a consular army and an area in which to campaign.

Military of ancient Rome

The military of ancient Rome, according to Titus Livius, one of the more illustrious historians of Rome over the centuries, was a key element in the rise of Rome over “above seven hundred years” from a small settlement in Latium to the capital of an empire governing a wide region around the shores of the Mediterranean, or, as the Romans themselves said, ‘’mare nostrum’’, “our sea.” Livy asserts

”... if any people ought to be allowed to consecrate their origins and refer them to a divine source, so great is the military glory of the Roman People that when they profess that their Father and the Father of their Founder was none other than Mars, the nations of the earth may well submit to this also with as good a grace as they submit to Rome's dominion.”Titus Flavius Josephus, a contemporary historian, sometime high-ranking officer in the Roman army, and commander of the rebels in the Jewish revolt, describes the Roman people as if they were "born ready armed." At the time of the two historians, Roman society had already evolved an effective military and had used it to defend itself against the Etruscans, the Italics, the Greeks, the Gauls, the maritime empire of Carthage, and the Macedonian kingdoms. In each war it acquired more territory until, when civil war ended the Roman Republic, nothing was left for the first emperor, Augustus, to do except declare it an empire and defend it.

The role and structure of the military was then altered during the empire. It became less Roman, the duties of border protection and territorial administration being more and more taken by foreign mercenaries officered by Romans. When they divided at last into warring factions the empire fell, unable to keep out invading armies.

’’ - an agency designated by 'SPQR' on public inscriptions. Its main body was the senate, which met in a building still extant in the forum of Rome. Its decrees were handed off to the two chief officers of the state, the consuls. They could levy from the citizens whatever military force they judged was necessary to execute such decree. This conscription was executed through a draft of male citizens assembled by age class. The officers of the legion were tasked with selecting men for the ranks. The will of the SPQR was binding on the consuls and the men, with the death penalty often assigned for disobedience or failure. The men were under a rigorous code, known now for its punitive crucifixion.

The consular duties were of any type whatever: military defense, police work, public hygiene, assistance in civil disaster, health work, agriculture, and especially construction of public roads, bridges, aqueducts, buildings, and the maintenance of such. The soldiers were kept busy doing whatever service needed to be done: soldiering, manning vessels, carpentry, blacksmithing, clerking, etc. They were trained as required, but also previous skills, such as a trade, were exploited. They brought to the task and were protected by the authority of the state.

The military's campaign history stretched over 1300 years and saw Roman armies campaigning as far east as Parthia (modern-day Iran), as far south as Africa (modern-day Tunisia) and Aegyptus (modern-day Egypt) and as far north as Britannia (modern-day England, south Scotland, and Wales). The makeup of the Roman military changed substantially over its history, from its early history as an unsalaried citizen militia to a later professional force, the Imperial Roman army. The equipment used by the military altered greatly in type over time, though there were very few technological improvements in weapons manufacture, in common with the rest of the classical world. For much of its history, the vast majority of Rome's forces were maintained at or beyond the limits of its territory, in order to either expand Rome's domain, or protect its existing borders. Expansions were infrequent, as the emperors, adopting a strategy of fixed lines of defense, had determined to maintain existing borders. For that purpose they constructed extensive walls and created permanent stations that became cities.

Roman army of the late Republic

The Roman army of the late Republic refers to the armed forces deployed by the late Roman Republic, from the beginning of the first century B.C. until the establishment of the Imperial Roman army by Augustus in 30 B.C.

Shaped by major social, political, and economic change, the late Republic saw the transition from the Roman army of the mid-Republic, which was a temporary levy based solely on the conscription of Roman citizens, to the Imperial Roman army of the Principate, which was a standing, professional army based on the recruitment of volunteers.Continuous expansion, wars, conflicts, and the acquisition of a growing, overseas territory led to an increasing degree of professionalism within the army. The late-Republic saw much of its action taking place within the Roman borders and between Roman commanders as they vied for control of the republic. There was a significant intertwining of military and politics in the acquisition and maintenance of power. After the Social War, and following the establishment of the First Triumvirate by Julius Caesar, Licinius Crassus, and Pompeius Magnus, there grew an emphasis on the expansion of a united republic toward regions such as Britain and Parthia. The effort to quell the invasions and revolts of non-Romans persisted throughout the period, from Marius’ battles with the wandering Germans in Italy to Caesar's campaign in Gaul.

After the completion of the Social War in 88 B.C., Roman citizenship was granted to all its Italian allies (the socii) south of the Po River. The alae were abolished, and the socii were from now on recruited directly into uniformly organized and equipped legions. The non-Italian allies that had long fought for Rome (e.g. Gallic and Numidian cavalry) continued to serve alongside the legions but remained irregular units under their own leaders.

For reasons that remain uncertain to this day, the structure of the Roman army changed dramatically during the late Republic. The maniple, which had been the standard unit throughout the mid-Republic, was replaced by the cohort as the new standard tactical unit of the legions, while the Roman citizen cavalry (equites) and light infantry (velites) disappeared from the battlefield. Traditionally, many of these changes have been attributed to the reforms of Gaius Marius (see Marian reforms), but some scholars argue that they may have happened far more gradually

Roman legion

A Roman legion (from Latin legio "military levy, conscription", from legere "to choose") was a large unit of the Roman army.

Structural history of the Roman military

The structural history of the Roman military concerns the major transformations in the organization and constitution of ancient Rome's armed forces, "the most effective and long-lived military institution known to history." From its origins around 800 BC to its final dissolution in AD 476 with the demise of the Western Roman Empire, Rome's military organization underwent substantial structural change. At the highest level of structure, the forces were split into the Roman army and the Roman navy, although these two branches were less distinct than in many modern national defense forces. Within the top levels of both army and navy, structural changes occurred as a result of both positive military reform and organic structural evolution. These changes can be divided into four distinct phases.

Phase I

The army was derived from obligatory annual military service levied on the citizenry, as part of their duty to the state. During this period, the Roman army would wage seasonal campaigns against largely local adversaries.Phase II

As the extent of the territories falling under Roman control expanded and the size of the forces increased, the soldiery gradually became salaried professionals. As a consequence, military service at the lower (non-salaried) levels became progressively longer-term. Roman military units of the period were largely homogeneous and highly regulated. The army consisted of units of citizen infantry known as legions (Latin: legiones) as well as non-legionary allied troops known as auxilia. The latter were most commonly called upon to provide light infantry, logistical, or cavalry support.Phase III

At the height of the Roman Empire's power, forces were tasked with manning and securing the borders of the vast provinces which had been brought under Roman control. Serious strategic threats were less common in this period and emphasis was placed on preserving gained territory. The army underwent changes in response to these new needs and became more dependent on fixed garrisons than on march-camps and continuous field operations.Phase IV

As Rome began to struggle to keep control over its sprawling territories, military service continued to be salaried and professional for Rome's regular troops. However, the trend of employing allied or mercenary elements was expanded to such an extent that these troops came to represent a substantial proportion of the armed forces. At the same time, the uniformity of structure found in Rome's earlier military disappeared. Soldiery of the era ranged from lightly armed mounted archers to heavy infantry, in regiments of varying size and quality. This was accompanied by a trend in the late empire of an increasing predominance of cavalry rather than infantry troops, as well as a requirement for more mobile operations. In this period there was more focus (on all frontiers but the east) on smaller units of independently-operating troops, engaging less in set-piece battles and more in low-intensity, guerilla actions.


Tribune (Latin: Tribunus) was the title of various elected officials in ancient Rome. The two most important were the tribunes of the plebs and the military tribunes. For most of Roman history, a college of ten tribunes of the plebs acted as a check on the authority of the senate and the annual magistrates, holding the power of ius intercessionis to intervene on behalf of the plebeians, and veto unfavourable legislation. There were also military tribunes, who commanded portions of the Roman army, subordinate to higher magistrates, such as the consuls and praetors, promagistrates, and their legates. Various officers within the Roman army were also known as tribunes. The title was also used for several other positions and classes in the course of Roman history.


A turma (Latin for "swarm, squadron", plural turmae) was a cavalry unit in the Roman army of the Republic and Empire. In the Byzantine Empire, it became applied to the larger, regiment-sized military-administrative divisions of a thema. The word is often translated as "squadron" but so is the term ala, a unit that was made up of several turmae.


The vexillum (; plural vexilla) was a flag-like object used as a military standard by units in the Ancient Roman army.

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