The Auxilia (Latin, lit. "auxiliaries") constituted the standing non-citizen corps of the Imperial Roman army during the Principate era (30 BC–284 AD), alongside the citizen legions. By the 2nd century, the Auxilia contained the same number of infantry as the legions and, in addition, provided almost all of the Roman army's cavalry (especially light cavalry and archers) and more specialised troops. The auxilia thus represented three-fifths of Rome's regular land forces at that time. Like their legionary counterparts, auxiliary recruits were mostly volunteers, not conscripts.

The Auxilia were mainly recruited from the peregrini, free provincial subjects who did not hold Roman citizenship and constituted the vast majority of the population in the 1st and 2nd centuries (c. 90% in the early 1st century). In contrast to the legions, which only admitted Roman citizens, members of the Auxilia could be recruited from territories outside of Roman control.

Reliance on the various contingents of non-Italic troops, especially cavalry, increased when the Roman Republic employed them in increasing numbers to support its legions after 200 BC. The Julio-Claudian period (30 BC–68 AD) saw the transformation of the Auxilia from motley levies to a standing corps with standardised structure, equipment and conditions of service. By the end of the period, there were no significant differences between legionaries and auxiliaries in terms of training, and thus, combat capability.

Auxiliary regiments were often stationed in provinces other than that in which they were originally raised, for reasons of security and to foster the process of Romanisation in the provinces. The regimental names of many auxiliary units persisted into the 4th century, but by then the units in question were different in size, structure, and quality from their predecessors.

Engineering corps traian s column river crossing
Roman auxiliary infantry crossing a river, probably the Danube, on a pontoon bridge during the emperor Trajan's Dacian Wars (AD 101–106). They can be distinguished by the oval shield (clipeus) they were equipped with, in contrast to the rectangular scutum carried by legionaries. Panel from Trajan's Column, Rome

Historical development

Background: Roman Republic (to 30 BC)

Arte etrusca, urna cineraria in terracotta con policromia forse autentica, 150 ac ca. 02
Etruscan funerary urn crowned with the sculpture of a woman and a front-panel relief showing two warriors fighting, polychrome terracotta, c. 150 BC

The mainstay of the Roman republic's war machine was the manipular legion, a heavy infantry unit suitable for close-quarter engagements on more or less any terrain, which was probably adopted sometime during the Samnite Wars (343–290 BC).[1] Despite its formidable strength, the legion had a number of deficiencies, especially a lack of cavalry. Around 200 BC, a legion of 4,200 infantry had a cavalry arm of only 300 horse (just 7% of the total force).[2] This was because the class of citizens who could afford to pay for their own horse and equipment – the equestrian order, the second rank in Roman society, after the senatorial order – was relatively small. In addition, the legion lacked missile forces such as slingers and archers.[3] Until 200 BC, the bulk of a Roman army's cavalry was provided by Rome's regular Italian allies (socii), commonly known as the "Latin" allies, which made up the Roman military confederation. This was Rome's defence system until the Social War of 91–88 BC. The Italian forces were organised into alae (literally: "wings", because they were generally posted on the flanks of the Roman line of battle). An allied ala, commanded by 3 Roman praefecti sociorum, was similar or slightly larger in infantry size (4–5,000 men) to a legion, but contained a more substantial cavalry contingent: 900 horse, three times the legionary contingent. Since a pre-Social War consular army always contained an equal number of legions and alae, 75% of its cavalry was provided by the Latin allies. The overall cavalry element, c. 12% of the total force (2,400 out of a normal consular army of approximately 20,000 total effectives), was greater than in most peninsular Italian forces, but well below the overall 21% cavalry component that was typical of the Principate army (80,000 cavalry out of 380,000 total effectives in the early 2nd century).[4][5]

The Roman/Latin cavalry was sufficient while Rome was in conflict with other states in the mountainous Italian peninsula, which also disposed of limited cavalry resources. But, as Rome was confronted by external enemies that deployed far more powerful cavalry elements, such as the Gauls and the Carthaginians, the Roman deficiency in cavalry numbers could be a serious liability, which in the Second Punic War (218–202 BC) resulted in crushing defeats. Hannibal's major victories at the Trebia and at Cannae, were owed to his Spanish and Gallic heavy cavalry, which far outnumbered the Roman and Latin levies, and to his Numidians, light, fast cavalry which the Romans wholly lacked.[6] The decisive Roman victory at Zama in 202 BC, which ended the war, owed much to the Numidian cavalry provided by king Massinissa, which outnumbered the Roman/Latin cavalry fielded by 2 to 1.[7] From then, Roman armies were always accompanied by large numbers of non-Italian cavalry: Numidian light cavalry and, later, Gallic heavy cavalry. For example, Caesar relied heavily on Gallic and German cavalry for his Conquest of Gaul (58–51 BC).[8]

As the role of native cavalry grew, that of Roman/Latin cavalry diminished. In the early 1st century BC, Roman cavalry was phased out altogether. After the Social War, the socii were all granted Roman citizenship, the Latin alae abolished, and the socii recruited into the legions.[9] Furthermore, Roman equestrians were no longer required to perform cavalry service after this time.[10] The late Republican legion was thus probably bereft of cavalry (a tiny cavalry force of 120 men was probably added back to the legion under Augustus).[11]

Slingers on Trajan's Column
Slingers from the cast of Trajan's Column in the Victoria and Albert Museum, London, 2nd century AD

By the outbreak of the Second Punic War, the Romans were remedying the legions' other deficiencies by using non-Italian specialised troops. Livy reports Hiero of Syracuse offering to supply Rome with archers and slingers in 217 BC.[12] From 200 BC onwards, specialist troops were hired as mercenaries on a regular basis: sagittarii (archers) from Crete, and funditores (slingers) from the Balearic Isles almost always accompanied Roman legions in campaigns all over the Mediterranean.[13]

The other main sources of non-Italian troops in the late Republic were subject provincials, allied cities and Rome's amici (satellite kings). During the late Republic, non-Italian units were led by their own native chiefs, and their internal organisation was left to their own commanders. The units varied widely in dress, equipment, and weapons. They were normally raised for specific campaigns and often disbanded soon afterwards, in a similar manner to the earlier socii militia legions.[14]

Foundation of the auxilia under Augustus (30 BC–14 AD)

It appears that not all indigenous units were disbanded at the end of the civil war period (31 BC). Some of the more experienced units were kept in existence to complement the legions, and became the core of the standing auxiliary forces that developed in the Julio-Claudian period.[15] During the early part of Augustus' rule (27 BC onwards), the corps of regular Auxilia was created. It was clearly inspired by the Latin forces of the pre-Social War Republic, as a corps of non-citizen troops parallel to the legions. But there were fundamental differences, the same as between Republican and Augustan legions. The Latin forces of the Republic were made up of part-time conscripts in units that would be raised and disbanded for and after particular campaigns. The Augustan Auxilia were mainly volunteer professionals serving in permanent units.[8]

The unit structure of the Auxilia also differed from the Latin alae, which were like legions with a larger cavalry arm. However, Augustus organised the Auxilia into regiments the size of cohorts (a tenth the size of legions), due to the much greater flexibility of the smaller unit size. Further, the regiments were of three types: ala (cavalry), cohors (peditata) (infantry) and cohors equitata (mixed cavalry/infantry).[16]

The evidence for the size of the Augustus' new units is not clearcut, with our most precise evidence dating to the 2nd century, by which time the unit strengths may have changed. Cohortes were likely modelled on legionary cohorts i.e. six centuriae of about 80 men each (total about 480 men).[17] Alae were divided into turmae (squadrons) of 30 (or 32) men, each under a decurio (literally: "leader of ten").[18] This title derives from the old Roman cavalry of the pre-Social War republic, in which each turma was under the command of three decuriones.[19] Cohortes equitatae were infantry cohortes with a cavalry contingent of four turmae attached.[20]

Auxiliary regiments were now led by a praefectus (prefect), who could be either a native nobleman, who would probably be granted Roman citizenship for the purpose (e.g. the famous German war leader Arminius gained Roman citizenship probably by serving as an auxiliary prefect before turning against Rome); or a Roman, either of knightly rank, or a senior centurion.[21]

At the start of Augustus' sole rule (30 BC), the original core auxiliary units in the West were composed of warlike tribesmen from the Gallic provinces (especially Gallia Belgica, which then included the regions later separated to form the provinces Germania Inferior and Germania Superior), and from the Balkan provinces (Dalmatia and Illyricum). By 19 BC, the Cantabrian and Asturian Wars were concluded, leading to the annexation of northern Hispania and Lusitania. Judging by the names of attested auxiliary regiments, these parts of the Iberian peninsula soon became a major source of recruits. Then the Danubian regions were annexed: Raetia (annexed 15 BC), Noricum (16 BC), Pannonia (9 BC) and Moesia (6 AD), becoming, with Illyricum, the Principate's most important source of auxiliary recruits for its entire duration. In the East, where the Syrians already provided the bulk of the Roman army's archers, Augustus annexed Galatia (25 BC) and Judaea: the former, a region in central Anatolia with a Celtic-speaking people, became an important source of recruits. In N. Africa, Egypt, Cyrene, and Numidia (25 BC) were added to the empire. Numidia (modern day Eastern Algeria) was home to the Numidians/Moors, the ancestors of today's Berber people. Their light cavalry (equites Maurorum) was highly prized and had alternately fought and assisted the Romans for well over two centuries: they now started to be recruited into the regular Auxilia. Even more Mauri units were formed after the annexation of Mauretania (NW Algeria, Morocco), the rest of the Berber homeland, in 44 AD by emperor Claudius (ruled 41–54).[22]

Recruitment was thus heavy throughout the Augustan period, with a steady increase in the number of units formed. By AD 23, the Roman historian Tacitus records that there were roughly the same numbers of auxiliaries in service as there were legionaries.[23] Since at this time there were 25 legions of c. 5,000 men each, the Auxilia thus amounted to c. 125,000 men, implying c. 250 auxiliary regiments.[24]

Illyrian revolt (6–9 AD)

During the early Julio-Claudian period, many auxiliary regiments raised in frontier provinces were stationed in or near their home provinces, except during periods of major crises such as the Cantabrian Wars, when they were deployed temporarily in theatre. This carried the obvious risk if their own tribe or ethnic group rebelled against Rome (or attacked the Roman frontier from outside the Empire), auxiliary troops could be tempted to make common cause with them. The Romans would then be faced by an enemy that included units fully equipped and trained by themselves, thus losing their usual tactical advantages over tribal foes.[25]

The German leader Arminius is the classic example at an individual level: after several years of serving in Rome's forces as prefect of an auxiliary unit, he used the military training and experience he had gained to lead a confederacy of German tribes against Rome, culminating in the destruction of three Roman legions in the Teutoberg Forest in 9 AD, and the abandonment of Augustus' strategy of annexing Germany as far as the Elbe river. (This strategy was never revived by later emperors).[26]

At a collective level, the risk was even greater, as the hugely dangerous Illyrian revolt proved. The central Illyrian tribes were tough and spartan shepherds of the Bosnian mountains and excellent soldier-material. Their territory formed part of the strategic province of Illyricum, recently expanded to include the territory of the Pannonii, Celticised Illyrian tribes based on the west bank of the Danube who were subjugated by Rome in 12–9 BC (the Bellum Pannonicum). By the start of the Common Era, they were an important recruitment base for the auxilia.[27] But discontent was festering among the Illyrian tribes, largely due to what they saw as the rapacity of Roman tax officials.[28] In AD 6, several regiments of Dalmatae, a warlike Illyrian tribe, were ordered to report to a designated location to prepare to join Augustus' stepson and senior military commander Tiberius in a war against the Germans. Instead, they mutinied at the assembly point, and defeated a Roman force sent against them.[29] The Dalmatae were soon joined by the Breuci, another Illyrian tribe that supplied several auxiliary regiments. They gave battle to a second Roman force from Moesia. They lost, but inflicted heavy casualties.[30] The rebels were now joined by a large number of other Illyrian tribes. The Dalmatae attacked the port of Salona and overran the Adriatic coast, defeating a Roman force and exposing the Roman heartland of Italy to the fear of a rebel invasion.[31]

Augustus ordered Tiberius to break off operations in Germany and move his main army to Illyricum.[32] When it became clear that even Tiberius' forces were insufficient, Augustus was obliged to raise a second task force under Tiberius' nephew Germanicus, resorting to the compulsory purchase and emancipation of thousands of slaves to find enough troops, for the first time since the aftermath of the Battle of Cannae over two centuries earlier.[33] The Romans had now deployed no less than 15 legions and an equivalent number of auxilia.[34] This amounts to a total of c. 150,000 men, including at least 50 auxiliary cohorts composed, exceptionally, of Roman citizens. These were men whose status or background was regarded by Augustus as unsuitable for recruitment into the legions: either natural-born citizens of the lowest category, including vagrants and convicted criminals, or the freed slaves (Roman law accorded citizenship to the freed slaves of Roman citizens). These special units were accorded the title civium Romanorum ("of Roman citizens"), or c.R. for short. After the Illyrian revolt, these cohorts remained in being and recruited non-citizens like other auxiliary units, but retained their prestigious c.R. title.[16][35] In addition, the regular forces were assisted by a large number of allied troops from neighbouring Thrace deployed by their king Rhoemetalces I, a Roman amicus (puppet king).[36]

The Romans faced further reverses on the battlefield and a savage guerrilla war in the Bosnian mountains.[37] It took them three years of hard fighting to quell the revolt, which was described by the Roman historian Suetonius, writing in c. AD 100, as the most difficult conflict faced by Rome since the Punic Wars over two centuries earlier.[34] Tiberius finally succeeded in quelling the revolt in 9 AD. This was apparently lucky timing for the Romans: that same year Arminius destroyed Varus' three legions in Germany. The Roman high command had no doubt that Arminius would have formed a grand alliance with the Illyrians.[38]

Despite the gravity of this rebellion, the Illyrians went on, alongside their neighbours the Thracians, to become the backbone of the Roman army. By the 2nd century, with roughly half the Roman army deployed on the Danube frontier, the auxilia and legions alike were dominated by Illyrian recruits. In the 3rd century, Illyrians largely replaced Italians in the senior officer echelons of praefecti of auxiliary regiments and tribuni militum of legions. Finally, from AD 268 to 379, virtually all emperors, including Diocletian and Constantine the Great were Romanised Illyrians from the provinces of Dalmatia, Moesia Superior and Pannonia. These were members of a military aristocracy, outstanding soldiers who saved the empire from collapse in the turbulent late 3rd century.[39]

Later Julio-Claudians (14–68 AD)

Roman helmet
The cavalry Witcham Gravel helmet from Cambridgeshire (England), 1st century AD

Significant development of the Auxilia appears to have taken place during the rule of the emperor Claudius (41–54 AD).

A minimum term of service of 25 years was established, at the end of which the retiring auxiliary soldier, and all his children, were awarded Roman citizenship.[40] This is deduced from the fact that the first known Roman military diplomas date from the time of Claudius. This was a folding bronze tablet engraved with the details of the soldier's service record, which he could use to prove his citizenship.[41] Claudius also decreed that prefects of auxiliary regiments must all be of equestrian rank, thus excluding centurions from such commands.[40] The fact that auxiliary commanders were now all of the same social rank as most tribuni militum, (military tribunes, a legion's senior staff officers, all of whom only one, the tribunus laticlavius, was of the higher senatorial rank), probably indicates that auxilia now enjoyed greater prestige. Indigenous chiefs continued to command some auxiliary regiments, and were probably granted equestrian rank for the purpose. It is also likely that auxiliary pay was standardised at this time, but we only have estimates for the Julio-Claudian period.[40]

Auxiliary uniform, armour, weapons and equipment were probably standardised by the end of the Julio-Claudian period. Auxiliary equipment was broadly similar to that of the legions (see Section 2.1 below for possible differences in armour). By 68 AD, there was little difference between most auxiliary infantry and their legionary counterparts in equipment, training and fighting capability. The main difference was that auxilia contained combat cavalry, both heavy and light, and other specialized units that legions lacked.[42]

Claudius annexed to the empire three regions that became important sources of auxiliary recruits: Britannia (43 AD), and the former client kingdoms of Mauretania (44) and Thracia (46). The latter became as important as Illyria as a source of auxiliary recruits, especially cavalry and archers. Britain in mid-2nd century contained the largest number of auxiliary regiments in any single province: about 60 out of about 400 (15%).[4] By the rule of Nero (54–68), auxiliary numbers may have reached, by one estimate, about 200,000 men, implying about 400 regiments.[40]

Revolt of the Batavi (69–70 AD)

Germania 70
Rhine frontier of the Roman empire, 70 AD, showing the location of the Batavi in the Rhine delta region. Roman territory is shaded dark. Their homeland was called the Insula Batavorum by the Romans and corresponded roughly with modern Gelderland province, Neth. Their chief town was Noviomagus (Nijmegen, Neth.), a strategic prominence in an otherwise flat and waterlogged land that became the site of a Roman legionary fortress (housing the legion X Gemina) after the Batavi revolt ended in 70 AD. The name is of Celtic origin, meaning "new market", suggesting that the Germanic Batavi either displaced or subjugated an indigenous Gallic tribe

The Batavi, a Germanic tribe, inhabited the region today known as Gelderland (Netherlands), in the Rhine river delta, then known as the Insula Batavorum ("Island of the Batavi", because surrounded by branches of the Rhine), part of the Roman province of Germania Inferior.[43] They were a warlike people, skilled horsemen, boatmen and swimmers. In return for the unusual privilege of exemption from tributum (direct taxes on land and heads normally exacted from peregrini), they supplied a disproportionate number of recruits to the Julio-Claudian auxilia: one ala and eight cohortes.[44] They also provided most of Augustus' elite personal bodyguard unit (the Germani corpore custodes), which continued in service until 68 AD. The Batavi auxilia amounted to about 5,000 men, implying that during the entire Julio-Claudian period, over 50% of all Batavi males reaching military age (16 years) may have enlisted in the auxilia.[45] Thus the Batavi, although just 0.05% of the total population of the empire of c. 70 million in 23 AD,[46] supplied about 4% of the total auxilia i.e. 80 times their proportionate share. They were regarded by the Romans as the very best (fortissimi, validissimi) of their auxiliary, and indeed all, their forces.[47] In Roman service, both their cavalry and infantry had perfected a technique for swimming across rivers wearing full armour and weapons.[48][49]

Julius Civilis (literally: "Julius the Citizen", clearly a Latin name adopted on gaining Roman citizenship, not his native one) was a hereditary prince of the Batavi and the prefect of a Batavi cohort. A veteran of 25 years' service, he had distinguished himself by service in Britain, where he and the eight Batavi cohorts had played a crucial role in both the Roman invasion in 43 AD and the subsequent subjugation of southern Britain.[50]

By 69, however, Civilis, the Batavi regiments and the Batavi people had become utterly disaffected with Rome. After the Batavi regiments were withdrawn from Britain to Italy in 66, Civilis and his brother (also a prefect) were arrested by the governor of Germania Inferior on a fabricated accusation of sedition. The governor ordered his brother's execution, while Civilis, who as a Roman citizen had the right to appeal to the emperor, was sent to Rome in chains for judgement by Nero.[51] He was released by Nero's overthrower and successor, Galba, but the latter also disbanded the imperial bodyguard unit for their loyalty to Nero. This alienated several hundred crack Batavi troops, and indeed the whole Batavi nation who regarded it as a grave insult.[52] At the same time, relations collapsed between the Batavi cohorts and the legion to which they had been attached since the invasion of Britain 25 years earlier (XIV Gemina). Their mutual hatred erupted in open fighting on at least two occasions.[53]

At this juncture, the Roman empire was convulsed by its first major civil war since the Battle of Actium exactly a century earlier: the Year of the Four Emperors (69–70 AD). The governor of Germania Inferior, ordered to raise more troops, outraged the Batavi by attempting to conscript more Batavi than the maximum stipulated in their treaty. The brutality and corruption of the Roman recruiting-centurions (including incidents of sexual assault on Batavi young men) brought already deep discontent in the Batavi homeland to the boil.[54]

Civilis now led his people in open revolt. Initially, he claimed he was supporting the bid for power of Vespasian, the general in command of the legions in Syria, whom Civilis had probably befriended when both were involved in the Roman invasion of Britain 25 years earlier (Vespasian was then commander of the legion II Augusta).[55] But the uprising soon became a bid for independence.[56] Civilis exploited the fact that some legions were absent from the Rhine area due to the civil war, and the rest under-strength. In addition, the Roman commanders and their rank-and-file soldiers were divided by loyalty to rival emperors.[57] Civilis quickly won the support of the Batavi's neighbours and kinsmen, the Cananefates, who in turn won over the Frisii. First the rebel allies captured two Roman forts in their territory, and a cohort of Tungri defected to Civilis.[58] Then two legions sent against Civilis were defeated when their companion Batavi ala defected to his side.[43] The Classis Germanica (Rhine flotilla), largely manned by Batavi, was seized by Civilis.[59] Most importantly, the 8 Batavi cohorts stationed at Mainz with XIV Gemina mutinied and joined him, defeating at Bonn a Roman force that attempted to block their return to their homeland.[60] By now, Civilis commanded at least 12 regiments (6,000 men) of Roman-trained and equipped auxiliary troops, as well as a much larger number of tribal levies. A number of German tribes from beyond the Rhine joined his cause.[61] Several other German and Gallic units sent against him deserted, as the revolt spread to the rest of Gallia Belgica, including the Tungri, Lingones and Treviri tribes.[62] He was able to destroy the two remaining legions in Germania Inferior, (V Alaudae and XV Primigenia).[63]

By this stage, Rome's entire position on the Rhine and even in Gaul was imperiled. Their civil war over, the Romans mustered a huge task force of eight legions (five dispatched from Italy, two from Spain and one from Britain) to deal with Civilis.[64] Its commander Petillius Cerialis had to fight two difficult battles, at Trier and Xanten, before he could overrun the Batavi's homeland.[65] Tacitus' surviving narrative breaks off as he describes a meeting on an island in the Rhine delta between Civilis and Cerialis to discuss peace terms.[66] We do not know the outcome of this meeting or Civilis' ultimate fate. But, in view of his former friendship with Vespasian, who had already offered him a pardon, and the fact that the Romans still needed the Batavi levies, it is likely that the terms were lenient by Roman standards.[67]

Petilius Cerialis took a number of reconstituted Batavi units with him to Britain, and the Batavi regiments continued to serve with special distinction in Britain and elsewhere for the rest of the 1st century and beyond.[68] Even as late as 395, units with the Batavi name, although long since composed of recruits from all over the empire, were still classified as elite palatini, e.g. the equites Batavi seniores (cavalry) and auxilium Batavi seniores (infantry).[69]

Flavian era (69–96 AD)

Grave for Titus Flavius Bassus Römisch-Germanisches Museum Cologne
Tombstone of the Flavian-era eques alaris (ala cavalryman) Titus Flavius Bassus, son of Mucala. A Dansala, (i.e. member of the Thracian Dentheletae tribe), he belonged to the Ala Noricorum (originally raised from the Taurisci tribe of Noricum). He died at age 46 after 26 years' service, not having advanced beyond the lowest rank. Bassus' adopted Roman names, Titus Flavius, indicate that he had gained Roman citizenship, doubtless by serving the required 25 years in the auxilia. The names adopted would normally be those of the emperor ruling at the time of the citizenship award. In this case, they could refer to any of the 3 emperors of the Flavian dynasty (ruled 69–96), Vespasian and his two sons, Titus and Domitian, all of whom carried the same names. The arrangement of the scene, a rider spearing a man (the motif of the Thracian Hero), indicates that Bassus was a Thracian, as does his father's name. Date: late 1st century. Römisch-Germanisches Museum, Cologne, Germany

The revolt of the Batavi appears to have led to a significant change in the Roman government's policy on deployment of Auxilia. The revolt proved that in times of civil strife, when legions were far from their bases campaigning for rival claimants to the imperial throne, it was dangerous to leave provinces exclusively in the hands of auxiliary regiments recruited from the indigenous nation. During the Julio-Claudian period, auxiliary regiments had often been deployed away from their original home province.[8] But in the Flavian period (69–96), this appears to have become standard policy.[25] Thus in AD 70, five reconstituted Batavi regiments (one ala and four cohortes) were transferred to Britain under Petillius Cerialis, who had suppressed the Civilis revolt and then embarked on the governorship of the island.[70] The great majority of regiments probably founded in the 1st century were stationed away from their province of origin in the second e.g. of 13 British regiments recorded in the mid-2nd century, none were stationed in Britain.[71] Furthermore, it appears that in the Flavian era native noblemen were no longer permitted to command auxiliary units from their own tribe.[72]

After a prolonged period in a foreign province a regiment would become assimilated, since the majority of its new recruits would be drawn from the province in which it was stationed, or neighbouring provinces.[25] Those same "British" units, mostly based on the Danube frontier, would by c. 150, after almost a century away from their home island, be largely composed of Illyrian, Thracian and Dacian recruits. However, there is evidence that a few regiments at least continued to draw some recruits from their original home provinces in the 2nd century e.g. Batavi units stationed in Britain.[73]

The Flavian period also saw the first formation of large, double-size units, both infantry and cavalry, of a nominal strength of 1,000 men (cohors/ala milliaria), though they were actually mostly smaller (720 for an ala milliaria and 800 for a cohors milliaria).[40] These were the mirror image of the double-strength first cohorts of legions also introduced at this time. Such units remained a minority of the Auxilia: in the mid-2nd century, they constituted 13% of units, containing 20% of total manpower.[74]

Later Principate (97–284)

Spatha end of second century 1
Roman cavalry spatha, a longer sword (median blade length: 780 mm [30.7 in]), designed to give the rider a longer reach than the gladius[75]

In 106 AD, emperor Trajan finally defeated the Dacian kingdom of Decebalus and annexed it as the Roman province of Dacia Traiana. By the mid-2nd century, there were 44 auxiliary regiments stationed there, about 10% of the total auxilia. In Britain, there were 60. Together, these two provinces contained about a quarter of the total auxiliary regiments.[4]

There is considerable scholarly dispute about the precise size of the auxilia during the imperial era, even during the corp's best-documented period, the rule of Trajan's successor, Hadrian (117–138). This is evident if one compares calculations by Spaul (2000) and Holder (2003):

Estimates of Roman auxilia numbers (units attested in the mid-2nd century)
Author No. Alae No. Cohortes Total no. units Total cavalry Total infantry Total effectives
J. Spaul (2000)[76] 80 247 327 56,160 124,640 180,800
P. A. Holder (2003)[4] 88 279 367 74,624 143,200 217,624

NOTE: Manpower figures exclude officers (centurions and decurions), which would have numbered about 3,500 men overall.

In addition, Holder believes that a further 14 cohortes, which are attested under Trajan, immediately before Hadrian's rule, but not during or after it, probably continued in existence, giving a total of 381 units and 225,000 effectives. The discrepancy between the two scholars is due to: (i) Interpretation of units with the same name and number, but attested in different provinces in the same period. Spaul tends to take a more cautious approach and to assume such are the same unit moving base frequently, while Holder tends to regard them as separate units which acquired the same number due to duplicated (or even triplicated) seriation. (ii) Assumptions about how many cohortes were equitatae. Spaul accepts only those cohortes specifically attested as equitatae i.e., about 40% of recorded units. Holder estimates that at least 70% of cohortes contained cavalry contingents by the early 2nd century[77]

Even according to the more conservative estimate, the auxilia were by this time significantly larger than the legions, which contained c. 155,000 effectives (28 legions of 5,500 men each) at this time, of which just 3,360 were cavalry. (For a detailed breakdown, see section 4: Auxilia deployment in the 2nd century, below).

During the second half of the 2nd century, the Roman army underwent considerable further expansion, with the addition of five new legions (27,500 men) to a Principate peak of 33.[78] A matching number of auxilia (i.e. c. 50 regiments, although only the names of around 25–30 have survived in the epigraphic record) were probably added, possibly reaching a peak of c. 440 regiments and around 250,000 effectives by the end of Septimius Severus's rule (211 AD).[5]

The likely growth of the Roman auxilia may be summarised as follows:

Estimated size of Roman army 24–305 AD
Army corps Tiberius
24 AD
c. 130 AD
S. Severus
211 AD
3rd-century crisis
c. 270 AD
LEGIONS 125,000[79] 155,000[80] 182,000[81]
AUXILIA 125,000[82] 218,000[83] 250,000[84]
Praetorian Guard ~~5,000[85] ~~8,000[86] ~15,000[86]
Total Roman Army 255,000[87] 381,000[88] 447,000[89] 290,000?[90] 390,000[91]

NOTE: Regular land forces only. Excludes citizen-militias, barbarian foederati, and Roman navy effectives

During the 2nd century, some units with the new names numerus ("group") and vexillatio ("detachment") appear in the diploma record.[92] Their size is uncertain, but was likely smaller than the regular alae and cohortes, as originally they were probably detachments from the latter, acquiring independent status after long-term separation. As these units are mentioned in diplomas, they were presumably part of the regular auxiliary organisation.[93] But numeri was also a generic term used for barbarian units outside the regular auxilia. (see section 2.4 Irregular units, below).

In 212, the constitutio Antoniniana (Antonine decree) of emperor Caracalla granted Roman citizenship to all the free inhabitants of the Empire – the peregrini – thus abolishing their second-class status.[94] But there is no evidence that the citizens-only rule for legions was also abolished at this time. The legions simply gained a much wider recruitment base, as they were now able to recruit any male free resident of the empire. Auxiliary units were now recruited mainly from Roman citizens, but probably continued to recruit non-citizen barbari from outside the Empire's borders.[95] However, the citizens-only rule for legions appears to have been dropped some time during the 3rd century, as by the 4th-century Romans and barbarians are found serving together in all units.[96]

In the mid to late 3rd century, the army was afflicted by a combination of military disasters and of pestilence, the so-called Crisis of the Third Century. In 251–271, Gaul, the Alpine regions and Italy, the Balkans and the East were simultaneously overrun by Alamanni, Sarmatians, Goths and Persians respectively.[97] At the same time, the Roman army was struggling with the effects of a devastating pandemic, probably of smallpox: the Plague of Cyprian, which began in 251 and was still raging in 270, when it claimed the life of emperor Claudius II Gothicus. The evidence for an earlier pandemic, the Antonine Plague (also smallpox) indicates a mortality of 15–30% in the empire as a whole.[98] The armies would likely have suffered deaths at the top end of the range, due to their close concentration of individuals and frequent movements across the empire.[99] This probably led to a steep decline in military numbers, which only recovered at the end of the century under Diocletian (r. 284–305).[100]

The recruitment shortfall caused by the crisis seems to have led to recruitment of barbarians to the auxilia on a much greater scale than previously. By the 4th century, it has been estimated that some 25% of regular army recruits were barbarian-born. In the elite palatini regiments, anywhere between a third and a half of recruits may have been barbarian.[96] This is likely a much greater proportion of foreigners than joined the auxilia in the 1st and 2nd centuries.[101] In the 3rd century, a small number of regular auxiliary units appear in the record that, for the first time, bear the names of barbarian tribes from outside the empire e.g. the ala I Sarmatarum attested in 3rd-century Britain.[102] This was probably an offshoot of the 5,500 surrendered Sarmatian horsemen posted on Hadrian's Wall by emperor Marcus Aurelius in c. 175.[103] This unit may be an early example of a novel process whereby irregular units of barbari (foederati) were transformed into regular auxilia. This process intensified in the 4th century: the Notitia Dignitatum, a key document on the late Roman army, lists a large number of regular units with barbarian names.[104]

4th century

Roman cavalry - Big Game Hunt mosaic - Villa Romana del Casale - Italy 2015
Roman cavalry from a mosaic of the Villa Romana del Casale, Sicily, 4th century AD

In the 4th century, the Roman army underwent a radical restructuring. In the rule of Diocletian (284–305), the traditional Principate formations of legiones, alae and cohortes appear to have been broken up into smaller units, many of which bore a variety of new names.[105] Under Constantine I (r. 312–337) it appears that military units were classified into three grades based on strategic role and to some extent quality: palatini, elite units normally part of the exercitus praesentales (imperial escort armies); comitatenses, higher-grade interception forces based in frontier provinces; and limitanei, lower-grade border troops.[106] (See Late Roman army).

The old Principate auxilia regiments provided the basis for units at all three grades. The Notitia Dignitatum lists about 70 alae and cohortes that retained their 2nd-century names, mostly limitanei.[107] But traces of other auxilia regiments can be found in the praesentales and comitatenses armies. For example, many of the new-style auxilia palatina infantry regiments, considered among the best units in the army, were probably formed from old-style auxiliary cohortes, which they appear to closely resemble.[108]

The late 4th-century writer on military affairs Vegetius complains of contemporary young men joining the "auxilia" in preference to the "legions" to avoid the latter's tougher training and duties.[109] But it is unclear what types of units he was referring to. It is possible that those older terms were still popularly used (misleadingly) to mean limitanei and comitatenses respectively. In any event, his quote in no way describes accurately the Principate auxilia, many of which were of very high quality.[16]

Unit types and structure

Regular unit types

The following table sets out the official, or establishment, strength of auxiliary units in the 2nd century. The real strength of a unit would fluctuate continually, but would likely have been somewhat less than the establishment most of the time.

Roman auxiliary regiments: Type, structure and strength[74]
Unit type Service Unit
No of
Ala quingenaria cavalry praefectus decurio 16 turmae 30 (32) 480 (512)
Ala milliaria cavalry praefectus decurio 24 turmae 30 (32) 720 (768)
Cohors quingenaria infantry praefectus* centurio 6 centuriae 80 480
Cohors milliaria infantry tribunus militum** centurio 10 centuriae 80 800
Cohors equitata
infantry plus
cavalry contingent
praefectus centurio (inf)
decurio (cav)
6 centuriae
4 turmae
(480 inf/120 cav)
Cohors equitata
infantry plus
cavalry contingent
tribunus militum** centurio (inf)
decurio (cav)
10 centuriae
8 turmae
(800 inf/240 cav)

* tribunus militum in original c.R. cohortes[110]
** praefectus in Batavi and Tungri cohortes milliariae[110]

NOTE: Opinion is divided about the size of an ala turma, between 30 and 32 men. 30 was the size of a turma in the Republican cavalry and in the cohors equitata of the Principate auxilia. Against this is a statement by Arrian that an ala was 512 strong.[111] This would make an ala turma 32 men strong.


These all-infantry units were modelled on the cohorts of the legions, with the same officers and sub-units. They were typically considered to be more of a light infantry than proper legionaries. Some auxiliaries may however have been equipped with the lorica segmentata, the most sophisticated legionary body-armour, although scholars dispute this.[112][113]

There is no evidence that auxiliary infantry fought in a looser order than legionaries.[16] It appears that in a set-piece battle-line, auxiliary infantry would normally be stationed on the flanks, with legionary infantry holding the centre e.g. as in the Battle of Watling Street (AD 60), the final defeat of the rebel Britons under queen Boudicca.[114] This was a tradition inherited from the Republic, when the precursors of auxiliary cohortes, the Latin alae, occupied the same position in the line.[115] The flanks of the line required equal, if not greater, skill to hold as the centre.


During the Principate period of the Roman Empire (30 BC – AD 284), the all-mounted alae ("wings") contained the elite cavalry of the army.[16] They were specially trained in elaborate manoeuvres, such as those displayed to the emperor Hadrian during a documented inspection in Numidia. They were best-suited for large-scale operations and battle, during which they acted as the primary cavalry escort for the legions, which had almost no cavalry of their own. Roman alares were normally armoured, with mail or scale body armour, a cavalry version of the infantry helmet (with more protective features, such as completely covered ears) and oval shield or hexagonal. Their weapons could be a lance, javelins, or bow and arrow but all Roman horseman had a sword called a (spatha) and the ubiquitous pugio. The elite status of an alaris is shown by the fact that he received 20% more pay than his counterpart in an auxiliary cohort or a legionary infantryman.

The favored sources of recruitment for the cavalry of the auxilia were Gauls, Germans, Iberians and Thracians. All of these peoples had long-established skills and experience of fighting from horseback – in contrast to the Romans themselves. The alae were better paid and mounted than the more numerous horsemen of the cohortes equitatae[116] (see below).

Cohortes equitatae

These were cohortes with a cavalry contingent attached. There is evidence that their numbers expanded with the passage of time. Only about 40% of attested cohortes are specifically attested as equitatae in inscriptions, which is probably the original Augustan proportion. A study of units stationed in Syria in the mid-2nd century found that many units that did not carry the equitata title did in fact contain cavalrymen e.g. by discovery of a tombstone of a cavalryman attached to the cohort. This implies that by that time, at least 70% of cohortes were probably equitatae.[77] The addition of cavalry to a cohort obviously enabled it to carry out a wider range of independent operations. A cohors equitata was in effect a self-contained mini-army.[117]

The traditional view of equites cohortales (the cavalry arm of cohortes equitatae), as expounded by G.L. Cheesman, was that they were just a mounted infantry with poor-quality horses. They would use their mounts simply to reach the battlefield and then would dismount to fight.[118] This view is today discredited. Although it is clear that equites cohortales did not match equites alares (ala cavalrymen) in quality (hence their lower pay), the evidence is that they fought as cavalry in the same way as the alares and often alongside them. Their armour and weapons were the same as for the alares.[119]

Nevertheless, non-combat roles of the equites cohortales differed significantly from the alares. Non-combat roles such as despatch-riders (dispositi) were generally filled by cohort cavalry.

Auxiliary specialised units

028 Conrad Cichorius, Die Reliefs der Traianssäule, Tafel XXVIII
Routed Sarmatian cataphracts (right) flee for their lives from Roman alares (auxiliary cavalrymen), during the Dacian Wars (AD 101–106). Note full-body scalar armour, also armoured caparison for horses (including eye-guards). The Sarmatians' lances (as well as the Romans') have disappeared due to stone erosion, but a sword is still visible, as is a bow carried by one man. It was apparently in the period following this conflict (perhaps as a result of the lessons learnt from it) that the Romans first established their own regular units of cataphracts, and deployed them in the Danubian region. They were most likely equipped as the Sarmatians. Panel from Trajan's Column, Rome
086 Conrad Cichorius, Die Reliefs der Traianssäule, Tafel LXXXVI
Roman archers (top left) in action. Note conical helmets, indicating Syrian unit, and recurved bows. Trajan's Column, Rome
047 Conrad Cichorius, Die Reliefs der Traianssäule, Tafel XLVII (Ausschnitt 03)
Roman slingers (funditores) in action in the Dacian Wars. Detail from Trajan's Column, Rome

In the Republican period, the standard trio of specialised auxilia were Balearic slingers, Cretan archers and Numidian light cavalry. These functions, plus some new ones, continued in the 2nd-century auxilia.

Equites cataphractarii, or simply cataphractarii for short, were the heavily armoured cavalry of the Roman army. Based on Sarmatian and Parthian models, they were also known as contarii and clibanarii, although it is unclear whether these terms were interchangeable or whether they denoted variations in equipment or role. Together with new units of light mounted archers, the cataphractarii were designed to counter Parthian (and, in Pannonia, Sarmatian) battle tactics. Parthian armies consisted largely of cavalry. Their standard tactic was to use light mounted archers to weaken and break up the Roman infantry line, and then to rout it with a charge by the cataphractarii concentrated on the weakest point.[120] The only special heavy cavalry units to appear in the 2nd-century record are: ala I Ulpia contariorum and ala I Gallorum et Pannoniorum cataphractaria stationed in Pannonia and Moesia Inferior respectively in the 2nd century.[121]

From the Second Punic War until the 3rd century AD, the bulk of Rome's light cavalry (apart from mounted archers from Syria) was provided by the inhabitants of the Maghrebi provinces of Africa and Mauretania Caesariensis, the Numidae or Mauri (from whom derives the English term "Moors"), who were the ancestors of the Berber people of modern Algeria and Morocco. They were known as the equites Maurorum or Numidarum ("Moorish or Numidian cavalry"). On Trajan's Column, Mauri horsemen, depicted with long hair in dreadlocks, are shown riding their small but resilient horses bare-back and unbridled, with a simple braided rope round their mount's neck for control. They wear no body or head armour, carrying only a small, round leather shield. Their weaponry cannot be discerned due to stone erosion, but is known from Livy to have consisted of several short javelins.[122][123] Exceptionally fast and maneuverable, Numidian cavalry would harass the enemy by hit-and-run attacks, riding up and loosing volleys of javelins, then scattering faster than any opposing cavalry could pursue. They were superbly suited to scouting, harassment, ambush and pursuit.[124] It is unclear what proportion of the Numidian cavalry were regular auxilia units as opposed to irregular foederati units.[125]

In the 3rd century, new formations of light cavalry appear, apparently recruited from the Danubian provinces: the equites Dalmatae ("Dalmatian cavalry"). Little is known about these, but they were prominent in the 4th century, with several units listed in the Notitia Dignitatum.

A unit of dromedarii ("camel-mounted troops") is attested from the 2nd century, the ala I Ulpia dromedariorum milliaria in Syria.[126]

A substantial number of auxiliary regiments (32, or about 1 in 12 in the 2nd century) were denoted sagittariorum, or archer-units (from sagittarii lit. "arrow-men", from sagitta = "arrow"). These 32 units (of which 4 were double-strength) had a total official strength of 17,600 men. All three types of auxiliary regiment (ala, cohors and cohors equitata) could be denoted sagittariorum. Although these units evidently specialised in archery, it is uncertain from the available evidence whether all sagittariorum personnel were archers, or simply a higher proportion than in ordinary units. At the same time, ordinary regiments probably also possessed some archers, otherwise their capacity for independent operations would have been unduly constrained. Bas-reliefs appear to show personnel in ordinary units employing bows.[127]

From about 218 BC onwards, the archers of the Roman army of the mid-Republic were virtually all mercenaries from the island of Crete, which boasted a long specialist tradition. During the late Republic (88–30 BC) and the Augustan period, Crete was gradually eclipsed by men from other, much more populous, regions subjugated by the Romans with strong archery traditions. These included Thrace, Anatolia and, above all, Syria. Of the 32 sagittarii units attested in the mid-2nd century, 13 have Syrian names, 7 Thracian, 5 from Anatolia, 1 from Crete and the remaining 6 of other or uncertain origin.[128]

Three distinct types of archers are shown on Trajan's Column: (a) with scalar cuirass, conical steel helmet and cloak; (b) without armour, with cloth conical cap and long tunic; or (c) equipped in the same way as general auxiliary foot-soldiers (apart from carrying bows instead of javelins). The first type were probably Syrian or Anatolian units; the third type probably Thracian.[129] The standard bow used by Roman auxilia was the recurved composite bow, a sophisticated, compact and powerful weapon.[127]

From about 218 BC onwards, the Republican army's slingers were exclusively mercenaries from the Balearic Islands, which had nurtured a strong indigenous tradition of slinging from prehistoric times. As a result, in classical Latin, Baleares (literally "inhabitants of the Balearic Islands") became an alternative word for "slingers" (funditores, from funda = "sling"). Because of this, it is uncertain whether the most of the imperial army's slingers continued to be drawn from the Balearics themselves, or, like archers, derived mainly from other regions.

Independent slinger units are not attested in the epigraphic record of the Principate.[127] However, slingers are portrayed on Trajan's Column. They are shown unarmoured, wearing a short tunic. They carry a cloth bag, slung in front, to hold their shot (glandes).[129]

Exploratores ('reconnaissance troops', from explorare = "to scout"). Two examples include numeri exploratorum attested to in the 3rd century in Britain: Habitanco and Bremenio (both names of forts).[130] It is possible, however, that more than 20 such units served in Britain.[131] The literal translation of numeri is 'numbers' and it was often used in the context of a generic title for any unit that was not of a standard size or structure. From the 2nd century onward they served as frontier guards, often supplied by the Sarmatians and the Germans.[132] Little else is known about such units.

Irregular allied forces

Throughout the Principate period, there is evidence of ethnic units of barbari outside the normal auxilia organisation fighting alongside Roman troops. To an extent, these units were simply a continuation of the old client-king levies of the late Republic: ad hoc bodies of troops supplied by Rome's puppet petty-kings on the imperial borders for particular campaigns. Some clearly remained in Roman service beyond the campaigns, keeping their own native leadership, attire and equipment and structure. These units were known to the Romans as socii ("allies"), symmachiarii (from symmachoi, Greek for "allies") or foederati ("treaty troops" from foedus, "treaty"). One estimate puts the number of foederati in the time of Trajan at about 11,000, divided into about 40 numeri (units) of about 300 men each. The purpose of employing foederati units was to use their specialist fighting skills.[133] Many of these would have been troops of Numidian cavalry (see light cavalry above).

The foederati make their first official appearance on Trajan's Column, where they are portrayed in a standardised manner, with long hair and beards, barefoot, stripped to the waist, wearing long trousers held up by wide belts and wielding clubs. In reality, several different tribes supported the Romans in the Dacian wars. Their attire and weapons would have varied widely. The Column stereotypes them with the appearance of a single tribe, probably the most outlandish-looking, to differentiate them clearly from the regular auxilia.[134] Judging by the frequency of their appearance in the Column's battle scenes, the foederati were important contributors to the Roman operations in Dacia. Another example of foederati are the 5,500 captured Sarmatian cavalrymen sent by Emperor Marcus Aurelius (r. 161–180) to garrison a fort on Hadrian's Wall after their defeat in the Marcomannic Wars.[135]

Recruitment, ranks and pay

The evidence for auxiliary ranks and pay is scant: even less exists than the patchy evidence for their legionary counterparts. There seems to be some consensus, however, that the auxiliary was paid one third of what a legionary received: 300 sesterces a year (400 after the reign of the emperor Commodus). Both auxiliaries and seamen received the viaticum of 300 sesterces, although the various sources differ as to whether auxiliaries and sailors received the retirement bonus[136] known as the honesta missio, or honorable discharge.[137][138]

The available data may be broken down and summarised as follows:

Auxilia ranks and pay (mid-1st century)[139]
Pay scale
(as multiple of basic)
Cohors infantry rank
(in ascending order)
XXX Ala rank
(in ascending order)
1 (caligati = "rankers") pedes (infantryman) 188 gregalis (ala cavalryman) 263
1.5 (sesquiplicarii = "one-and-half-pay men") tesserarius (corporal) 282 sesquiplicarius (corporal) 395
2 (duplicarii = "double-pay men") signifer (centuria standard-bearer)
optio (centurion's deputy)
vexillarius (cohort standard-bearer)
376 signifer (turma standard-bearer)
curator? (decurion's deputy)
vexillarius (ala standard-bearer)
Over 5 centurio (centurion = centuria commander)
centurio princeps (chief centurion)
beneficiarius? (deputy cohort commander)
940 + decurio (decurion = turma commander)
decurio princeps (chief decurion)
beneficiarius? (deputy ala commander)
1,315 +
50 praefectus or tribunus (cohort commander) 9,400 praefectus or tribunus (ala commander) 13,150

Rankers (caligati)

Tombstone of Marius son of Ructicnus. The inscription states that he was a miles (ranker) of the Alpine infantry regiment Cohors I Montanorum, who died in his 25th year of service (i.e. in the final year of the minimum term for an auxiliary and just before qualifying for Roman citizenship). His heir, who erected the stone, is named Montanus, the same ethnic name as the regiment's, meaning a native of the eastern Alps, most likely the origin of the deceased. Note (top corners) the Alpine edelweiss flowers, called stella Alpina ("Alpine star") in Latin. These were either a regimental symbol, or a national symbol of the Montani. The crescent moon-and-star motif between the flowers may be either a regimental emblem or a religious symbol. Date: 1st century, probably ante 68. From Carinthia, Austria

At the bottom end of the rank pyramid, rankers were known as caligati (lit: "sandal men" from the caligae or hob-nailed sandals worn by soldiers). Depending on the type of regiment they belonged to, they held the official ranks of pedes (foot soldier in a cohors), eques (cavalryman in a cohors equitata) and gregalis (ala cavalryman).[140]

During the Principate, recruitment into the legions was restricted to Roman citizens only. This rule, which derived from the pre-Social War Republican army, was strictly enforced. The few exceptions recorded, such as during emergencies and for the illegitimate sons of legionaries, do not warrant the suggestion that the rule was routinely ignored.[141]

In the 1st century, the vast majority of auxiliary common soldiers were recruited from the Roman peregrine (second-class citizens). In the Julio-Claudian era, conscription of peregrini seems to have been practiced alongside voluntary recruitment, probably in the form of a fixed proportion of men reaching military age in each tribe being drafted.[142] From the Flavian era onwards, the auxilia were an all-volunteer force.[143] Although recruits as young as 14 are recorded, the majority of recruits (66%) were from the 18–23 age group.[144]

When it was first raised, an auxiliary regiment would have been recruited from the native tribe or people whose name it bore. In the early Julio-Claudian period, it seems that efforts were made to preserve the ethnic integrity of units, even when the regiment was posted in a faraway province. But in the later part of the period, recruitment in the region where the regiment was posted increased and became predominant from the Flavian era onwards.[142] The regiment would thus lose its original ethnic identity.[25] The unit's name would thus become a mere curiosity devoid of meaning, although some of its members might inherit foreign names from their veteran ancestors. This view has to be qualified, however, as evidence from military diplomas and other inscriptions shows that some units continued to recruit in their original home areas e.g. Batavi units stationed in Britain, where some units had an international membership.[73] It also appears that the Danubian provinces (Raetia, Pannonia, Moesia, Dacia) remained key recruiting grounds for units stationed all over the empire.[145][146]

It appears that Roman citizens were also regularly recruited to the auxilia. Most likely, the majority of citizen recruits to auxiliary regiments were the sons of auxiliary veterans who were enfranchised on their fathers' discharge.[147] Many such may have preferred to join their fathers' old regiments, which were a kind of extended family to them, rather than join a much larger, unfamiliar legion. There are also instances of legionaries transferring to the auxilia (to a higher rank).[148] The incidence of citizens in the auxilia would thus have grown steadily over time until, after the grant of citizenship to all peregrini in 212, auxiliary regiments became predominantly, if not exclusively, citizen units.

Less clearcut is the question of whether the regular auxilia recruited barbari (barbarians, as the Romans called people living outside the empire's borders). Although there is little evidence of it before the 3rd century, the consensus is that auxilia recruited barbarians throughout their history.[95][149] In the 3rd century, a few auxilia units of clearly barbarian origin start to appear in the record e.g. Ala I Sarmatarum, cuneus Frisiorum and numerus Hnaufridi in Britain.[150][151]

There existed a hierarchy of pay between types of auxiliary, with cavalry higher paid than infantry. One recent estimate is that in the time of Augustus, the annual pay structure was: eques alaris (gregalis) 263 denarii, eques cohortalis 225, and cohors infantryman 188.[152] The same differentials (of about 20% between grades) seem to have existed at the time of Domitian (r. 81–96).[153] However, Goldsworthy points out that the common assumption that rates of pay were universal across provinces and units is unproven. Pay may have varied according to the origin of the unit.[154]

The remuneration of an auxiliary pedes cohortalis may be compared to a legionary's as follows:

Remuneration of Roman common foot soldiers (about AD 70)[155]
legionary pedes:
amount (denarii)
XXX auxiliary pedes
amount (denarii)
Stipendium (gross salary) 225 188
Less: Food deduction 60 60
Less: Equipment etc. deductions 50 50
Net disposable pay 115 78
Plus: Donativa (bonuses)
(average: 75 denarii every 3 years)
25 none proven
Total disposable income 140 78
Praemia (discharge bonus: 3,000 denarii) 120 none proven

Gross salary was subject to deductions for food, clothing, boots and hay (probably for the company mules). It is unclear whether the cost of armour and weapons was also deducted, or borne by the army. Deductions left the soldier with a net salary of 78 denarii. This sum was sufficient, on the basis of the food deduction, to amply feed an adult for a year. In 84 AD Domitian increased basic legionary pay by 33% (from 225 to 300 denarii): a similar increase was presumably accorded to auxiliaries, boosting their net income to 140 denarii, i.e. more than two food allowances.[156] It was entirely disposable, as the soldier was exempt from the poll tax (capitatio), did not pay rent (he was housed in fort barracks) and his food, clothing and equipment were already deducted. It should be borne in mind that most recruits came from peasant families living at subsistence level. To such persons, any disposable income would appear attractive.[157] It could be spent on leisure activities, sent to relatives or simply saved for retirement.

There is no evidence that auxiliaries received the substantial cash bonuses (donativum) handed to legionaries on the accession of a new emperor and other occasions.[158] Although irregular, these payments (each worth 75 denarii to a common legionary) averaged once every 7.5 years in the early 1st century and every three years later. Duncan-Jones has suggested that donativa may have been paid to auxiliaries also from the time of Hadrian onwards, on the grounds that the total amount of donative to the military increased sharply at that time.[159] A very valuable benefit paid to legionaries was the discharge bonus (praemia) paid on completion of the full 25 years' service. At 3,000 denarii, this was equivalent to ten years' gross salary for a common legionary after the pay increase of 84 AD. It would enable him to purchase a substantial plot of land. Again, there is no indication that auxiliaries were paid a discharge bonus. For auxiliaries, the discharge bonus was the grant of Roman citizenship, which carried important tax exemptions. However, Duncan-Jones argues that the fact that service in the auxilia was competitive with the legions (deduced from the many Roman citizens that joined the auxilia) that a discharge bonus may have been paid.[160]

Junior officers (principales)

Below centurion/decurion rank, junior officers in the Roman army were known as principales. An auxiliary cohort's ranks appear the same as in a legionary centuria. These were, in ascending order: tesserarius ("officer of the watch"), signifer (standard-bearer for the centuria), optio (centurion's deputy) and vexillarius (standard-bearer for the whole regiment, from vexillum). In the turmae of cohortes equitatae (and of alae?), the decurion's second-in-command was probably known as a curator, responsible for horses and caparison.[161] As in the legions, the principales, together with some regimental specialists, were classified in two pay-scales: sesquiplicarii ("one-and-a-half-pay men") and duplicarii ("double-pay men").[152] These ranks are probably most closely resembled by the modern ranks of corporal and sergeant respectively.

Besides combat effectives, regiments also contained specialists, the most senior of whom were sesquiplicarii or duplicarii, the rest common soldiers with the status of milities immunes ("exempt soldiers" i.e. exempt from normal duties). Ranking specialists included the medicus (regimental doctor), veterinarius (veterinary doctor, in charge of the care of horses, pack animals and livestock), custos armorum (keeper of the armoury), and the cornicularius (clerk in charge of all the regiment's records and paperwork).[162]

Senior officers

Grabstein Titus Calidius Carnuntum
Tombstone of Titus Calidius Severus, a Roman cavalryman. The career summary in the inscription shows that Severus joined the auxiliary regiment cohors I Alpinorum, rising from eques (common cavalryman) through optio to decurion. He then switched to a legion (presumably after gaining Roman citizenship after 25 of his 34 years of service) and became a centurion in Legio XV Apollinaris (it appears that legion cavalrymen used infantry ranks). He died at age 58, probably a few years after his discharge. Note the portrayal of his chain-mail armour, centurion's transverse-crested helmet and his horse, led by his equerry, probably a slave. This soldier's long career shows that many auxiliaries served longer than the minimum 25 years, and sometimes joined legions. Erected by his brother, Quintus. Dates from ante 117, when XV Apollinaris was transferred from Carnuntum (Austria) to the East

The limited evidence on auxiliary centuriones and decuriones is that such officers could be directly commissioned as well as promoted from the ranks. Many appear to have come from provincial aristocracies.[163] Those rising from the ranks could be promotions from the legions as well as from the regiment's own ranks. In the Julio-Claudian period auxiliary centuriones and decuriones were a roughly equal split between citizens and peregrini, though later citizens became predominant due to the spread of citizenship among military families.[148] Because centuriones and decuriones often rose from the ranks, they have often been compared to warrant officers such as sergeants-major in modern armies. However, centurions' social role was much wider than a modern warrant-officer. In addition to their military duties, centurions performed a wide range of administrative tasks, which was necessary in the absence of an adequate bureaucracy to support provincial governors. They were also relatively wealthy, due to their high salaries (see table above).[164] However, most of the surviving evidence concerns legionary centurions and it is uncertain whether their auxiliary counterparts shared their high status and non-military role.[163]

There is little evidence about the pay-scales of auxiliary centuriones and decuriones, but these are also believed to have amounted to several times that of a miles.[164]

Unlike a legatus legionis (who had an officer staff of 6 tribuni militum and one praefectus castrorum), an auxiliary praefectus does not appear to have enjoyed the support of purely staff officers. The possible exception is an attested beneficiarius ("deputy"), who may have been the praefectus' second-in-command, if this title was a regular rank and not simply an ad hoc appointment for a specific task. Also attached to the praefectus were the regiment's vexillarius (standard-bearer for the whole unit) and cornucen (horn-blower).[161]


From a survey by Devijver of persons whose origin can be determined, it appears that during the 1st century, the large majority (65%) of auxiliary prefects were of Italian origin. The Italian proportion dropped steadily, to 38% in the 2nd century, and 21% in the 3rd century.[165] From the time of emperor Claudius (r. 41–54) only Roman knights were eligible to hold command of an auxiliary regiment. This status could be obtained either by birth (i.e. if the person was the son of a hereditary Roman knight; or by attaining the property qualification (100,000 denarii, the equivalent of 400 years' gross salary for an auxiliary alaris); or by military promotion: the latter were the chief centurions of legions (centurio primus pilus) who would normally be elevated to equestrian rank by the emperor after completing their single-year term as primuspilus.[166]

Equestrians by birth would normally begin their military careers at c. 30 years of age. An axillary had to do 25 years of service before joining the army. Commands were held in a set sequence, each held for 3–4 years: prefect of an auxiliary cohors, tribunus militum in a legion and finally prefect of an auxiliary ala. In Hadrian's time, a fourth command was added, for exceptionally able officers, of prefect of an ala milliaria. Like officers senatorial rank, hereditary equestrians held civilian posts before and after their decade of military service, whereas non-hereditary officers tended to remain in the army, commanding various units in various provinces. By the 3rd century, most auxiliary prefects had exclusively military careers.[166][167]

The pay of a praefectus of an auxiliary regiment in the early 2nd century has been estimated at over 50 times that of a miles (common soldier).[110] (This compares to a full colonel in the British Army, who is currently paid about five times a private's salary).[168] The reason for the huge gap between the top and the bottom of the pyramid is that Roman society was far more hierarchical than a modern one. A praefectus was not just a senior officer. He was also a Roman citizen (which most of his men were not) and, as a member of the equestrian order, an aristocrat. The social gulf between the praefectus and a peregrinus soldier was thus immense, and the pay differential reflected that fact.

Names, titles and decorations

Regimental names

The nomenclature of the great majority of regiments followed a standard configuration: unit type, followed by serial number, followed by name of the peregrini tribe (or nation) from whom the regiment was originally raised, in the genitive plural case e.g. cohors III Batavorum ("3rd Cohort of Batavi"); cohors I Brittonum ("1st Cohort of Britons"). Some regiments combine the names of two peregrini tribes, most likely after the merger of two previously separate regiments e.g. ala I Pannoniorum et Gallorum ("1st Wing of Pannonii and Gauls"). A minority of regiments are named after an individual, mostly after the first prefect of the regiment, e.g. ala Sulpicia (presumably named after a prefect whose middle (gens) name was Sulpicius). The latter is also an example of a regiment that did not have a serial number.[169]


Regiments were often rewarded for meritorious service by the grant of an honorific title. The most sought-after was the prestigious c.R. (civium Romanorum = "of Roman citizens") title. In the latter case, all the regiment's members at the time, but not their successors, would be granted Roman citizenship. But the regiment would retain the c.R. title in perpetuity. Another common title was the gens name of the emperor making the award (or founding the regiment) e.g. Ulpia: the gens name of Trajan (Marcus Ulpius Traianus r.98–117). Other titles were similar to those given to the legions e.g. pia fidelis (p.f. = "dutiful and loyal").[170]


The Roman army awarded a variety of individual decorations (dona) for valour to its legionaries. Hasta pura was a miniature spear; phalerae were large medal-like bronze or silver discs worn on the cuirass; armillae were bracelets worn on the wrist; and torques were worn round the neck, or on the cuirass. The highest awards were the coronae ("crowns"), of which the most prestigious was the corona civica, a crown made of oak-leaves awarded for saving the life of a Roman citizen in battle. The most valuable award was the corona muralis, a crown made of gold awarded to the first man to scale an enemy rampart. This was awarded rarely, as such a man hardly ever survived.[158]

There is no evidence that auxiliary common soldiers received individual decorations, although auxiliary officers did. Instead, the whole regiment was honoured by a title reflecting the type of award e.g. torquata (awarded a torque) or armillata (awarded bracelets). Some regiments would, in the course of time, accumulate a long list of titles and decorations e.g. cohors I Brittonum Ulpia torquata pia fidelis c.R..[170]

Deployment in the 2nd century

Imperial auxilia: Summary of known deployments c. 130 AD[171]
Province Approx. modern
(no. mill.)
(no. mill.)
aux. units
Britannia England/Wales 11 (1) 45 (6) 56 25,520 10,688 36,208
Rhine Frontier
Germania Inferior S Neth/NW Rhineland 6 17 23 8,160 4,512 12,672
Germania Superior Pfalz/Alsace 3 22 (1) 25 10,880 3,336 14,216
Danube Frontier
Raetia/Noricum S Ger/Switz/Austria 7 (1) 20 (5) 27 11,220 5,280 16,500
Pannonia (Inf + Sup) W Hungary/Slovenia/Croatia 11 (2) 21 (4) 32 11,360 8,304 19,664
Moesia Superior Serbia 2 10 12 4,800 1,864 6,664
Moesia Inferior N Bulgaria/coastal Rom 5 12 17 5,760 3,520 9,280
Dacia (Inf/Sup/Poroliss) Romania 11 (1) 32 (8) 43 17,920 7,328 25,248
Eastern Frontier
Cappadocia Central/East Turkey 4 15 (2) 19 7,840 3,368 11,208
Syria (inc Judaea/Arabia) Syria/Leb/Palest/Jordan/Israel 12 (1) 43 (3) 55 21,600 10,240 31,840
North Africa
Aegyptus Egypt 4 11 15 5,280 3,008 8,288
Mauretania (inc Africa) Tunisia/Algeria/Morocco 10 (1) 30 (1) 40 14,720 7,796 22,516
Internal provinces 2 15 17 7,200 2,224 9,424
Total Empire 88 (7) 293 (30) 381 152,260 71,468 223,728
Roman Empire 125
Roman Empire during Hadrian's reign (AD 125)

Notes: (1) Table excludes about 2,000 officers (centurions and above). (2) Auxiliary cavalry nos. assumes 70% of cohortes were equitatae


  1. The table shows the importance of auxiliary troops in the 2nd century, when they outnumbered legionaries by 1.5 to 1.
  2. The table shows that legions did not have a standard complement of auxiliary regiments[172] and that there was no fixed ratio of auxiliary regiments to legions in each province. The ratio varied from six regiments per legion in Cappadocia to 40 per legion in Mauretania.
  3. Overall, cavalry represented about 20% (including the small contingents of legionary cavalry) of the total army effectives. But there were variations: in Mauretania the cavalry proportion was 28%.
  4. The figures show the massive deployments in Britannia and Dacia. Together, these two provinces account for 27% of the total auxilia corps.

See also


  1. ^ Goldsworthy (2000) 44
  2. ^ Goldsworthy (2000) 51
  3. ^ Goldsworthy (2000) 49
  4. ^ a b c d Holder (2003) 145
  5. ^ a b Hassall (2000) 320
  6. ^ Goldsworthy (2000) 74–5
  7. ^ Goldsworthy (2000) 78–9
  8. ^ a b c Goldsworthy (2000) 126
  9. ^ Goldsworthy (2000) 107
  10. ^ Keppie (1996) 372
  11. ^ Keppie (196) 375
  12. ^ Livy Ab Urbe Condita XXII.37
  13. ^ G.L. Cheesman, The Auxilia of the Roman Imperial Army (Oxford, 1914), 8–9.
  14. ^ Keppie (1996) 373
  15. ^ Keppie (1996) 379
  16. ^ a b c d e Goldsworthy (2000) 127
  17. ^ Holder (1980) 7
  18. ^ Goldsworthy (2000) 214
  19. ^ Goldsworthy (2003) 27
  20. ^ Holder (1980) 9
  21. ^ Keppie (1996) 382
  22. ^ Holder (1982) 110–3
  23. ^ Tacitus Annales IV.5
  24. ^ Goldsworthy (2003) 51
  25. ^ a b c d Keppie (1996) 396
  26. ^ Goldsworthy (2000) 119
  27. ^ Holder (1982) 145
  28. ^ Dio LV.29.1
  29. ^ Dio LV.29.2
  30. ^ Dio LV.29.3
  31. ^ Dio LV.29.4
  32. ^ Dio LV.30.1
  33. ^ Dio LV.31.1
  34. ^ a b Suetonius III.16
  35. ^ Goldsworthy (2003) 64
  36. ^ Dio LV.30.6
  37. ^ Dio LV.30.5
  38. ^ Suetonius III.17
  39. ^ Goldsworthy (2000) 165–6
  40. ^ a b c d e Keppie (1996) 391
  41. ^ Archived 2014-01-05 at the Wayback Machine Military Diplomas Online Introduction
  42. ^ Keppie (1996) 390
  43. ^ a b Tacitus Historiae IV.18
  44. ^ Tacitus Historiae IV.12
  45. ^ Birley (2002) 43
  46. ^ Scheidel (2006) 9
  47. ^ Tacitus Germania 29.1 and Historiae II.28
  48. ^ Dio Cassius LXIX.9.6
  49. ^ Tacitus Historiae IV.12
  50. ^ Tacitus Annales IV.12
  51. ^ Tacitus Historiae IV.13
  52. ^ Tacitus Historiae II.5
  53. ^ Tacitus Historiae I.64, II.66
  54. ^ Tacitus Historiae IV.14
  55. ^ Tacitus Historiae IV.13
  56. ^ Tacitus Historiae IV.54
  57. ^ Tacitus Historiae IV.24, 27
  58. ^ Tacitus Historiae IV.15–6
  59. ^ Tacitus Historiae IV.16
  60. ^ Tacitus Historiae IV.20
  61. ^ Tacitus Historiae IV.21, 28
  62. ^ Tacitus Historiae IV.33, 66, 67
  63. ^ Tacitus Historiae
  64. ^ Tacitus Historiae IV.68
  65. ^ Tacitus Historiae V
  66. ^ Tacitus Historiae V.26
  67. ^ Birley (2002) 44
  68. ^ Tacitus Agricola 35–8
  69. ^ Notitia Dignitatum Titles IV and V
  70. ^ Mattingly (2006) 132
  71. ^ Roxan (2003); Holder (2006)
  72. ^ Keppie (1996) 394
  73. ^ a b Mattingly (2006) 168–9
  74. ^ a b Hassall (2000) 332–4
  75. ^ Goldsworthy (2003) 138
  76. ^ Spaul (2000) 526
  77. ^ a b Holder (2003), p. 119
  78. ^ Goldsworthy (2000) 152 (map): Legiones II and III Italica under Marcus Aurelius (r. 161–80) and I, II and III Parthica under Septimius Severus (r. 197–211)
  79. ^ 25 legions of 5,000 men each
  80. ^ 28 legions of 5,500 each (double-strength 1st cohorts introduced under Domitian (r. 81–96)
  81. ^ Goldsworthy (2000) 152 (map): 33 legions of 5,500 each
  82. ^ Tacitus Annales IV.5
  83. ^ Holder (2003) 120
  84. ^ J. C. Spaul ALA (1996) 257–60 and COHORS 2 (2000) 523–7 identify 4 alae and 20–30 cohortes raised in the late 2nd/early 3rd centuries
  85. ^ Goldsworthy (2003) 58: 9 cohorts of 480 men each plus German bodyguards
  86. ^ a b Rankov (1994) 8
  87. ^ Implied by Tacitus Annales
  88. ^ Hassall (2000) 320 estimates 380,000
  89. ^ MacMullen How Big was the Roman Army? in KLIO (1979) 454 estimates 438,000
  90. ^ Assuming 33% drop in nos. due to war/disease
  91. ^ John Lydus De Mensibus I.47
  92. ^ Holder (2006) 985; Roxan (2003) 672
  93. ^ Campbell (2005) 212
  94. ^ The Roman Law Library Constitutio Antoniniana de Civitate
  95. ^ a b Goldsworthy (2003) 74
  96. ^ a b Elton (1996) 148–52
  97. ^ Goldsworthy (2000) 162
  98. ^ D. Ch. Stathakopoulos Famine and Pestilence in the late Roman and early Byzantine Empire (2007) 95
  99. ^ Zosimus New History 26, 37, 46
  100. ^ MacMullen (1979) 455
  101. ^ Lee (1997) 223
  102. ^ Archived 2003-12-17 at the Wayback Machine list of alae
  103. ^ Dio LXXI
  104. ^ Jones (1964) 620
  105. ^ Goldsworthy (2003) 206
  106. ^ Jones (1964) 610
  107. ^ Notitia Dignitatum passim
  108. ^ Goldsworthy (2000) 174
  109. ^ Vegetius III.3
  110. ^ a b c Birley (2002) 46
  111. ^ Arrian Ars Tactica 17.3
  112. ^ Hassall (2000) 339
  113. ^ Goldsworthy (2003) 136
  114. ^ Goldsworthy (2003), pp. 52–53
  115. ^ Goldsworthy (2000), p. 52
  116. ^ Fields, Nic. Boudicca's Rebellion AD 60–61. p. 38. ISBN 978-1-84908-313-3.
  117. ^ Goldsworthy (2003), p. 168
  118. ^ Cheesman (1914)
  119. ^ Davies (1988), pp. 141–143
  120. ^ Goldsworthy (2000), p. 140
  121. ^ Holder (2003), pp. 135, 133
  122. ^ Livy XXXV.12
  123. ^ Rossi (1971), p. 104
  124. ^ Sidnell (2006), p. 172
  125. ^ CAH XII 212
  126. ^ Holder (2003), p. 140
  127. ^ a b c Goldsworthy (2003), p. 137
  128. ^ Holder (2003)
  129. ^ a b Rossi (1971), p. 102
  130. ^ Mattingly, 2006, 223
  131. ^ Holder, The Roman Army in Britain Batsford, 1982.
  132. ^ Dando-Collins, The Legions of Rome, pp40, Quercus (2010).
  133. ^ Grant (1985), p. 72
  134. ^ Rossi (1971), p. 104.
  135. ^ Dio Cassius LXXI.16
  136. ^ Starr, Imperial Roman Navy, 31BC-AD324 Westport, 1975.
  137. ^ Gardiner 2000, p. 80
  138. ^ Morris, Londinium, pp44, Book Club Associates, 1982
  139. ^ Based on data in Goldsworthy (2003) 95–5; Holder (1980) 86–96; Elton (1996) 123
  140. ^ Davies (1988) 148
  141. ^ Goldsworthy (2003) 78, 80
  142. ^ a b Holder (1980) 123
  143. ^ Goldsworthy (2003) 76
  144. ^ Holder (1980) 138
  145. ^ Military Diplomas Online Introduction
  146. ^ RMD Vol V Appendix 4 e.g. RMD 127, 128
  147. ^ Mattingly (2006) 190
  148. ^ a b Holder (1980) 86–8
  149. ^ Heather (2005) 119
  150. ^ Mattingly (2006) 223
  151. ^ Archived 2003-12-17 at the Wayback Machine List of auxiliary units in Britain
  152. ^ a b Goldsworthy (2003) 94
  153. ^ Hassall (2000) 336
  154. ^ Goldsworthy (2003) 95
  155. ^ Based on figs in Goldsworthy (2003) 94; Duncan-Jones (1994) 33–41
  156. ^ Duncan-Jones (1994) 34
  157. ^ Jones (1964) 647
  158. ^ a b Goldsworthy (2003) 96
  159. ^ Duncan-Jones (1994) 40
  160. ^ Duncan-Jones (1994) 36
  161. ^ a b Birley (2002) 47
  162. ^ Birley (2002) 47–8; Vindolanda Tablets Online Introduction: Personnel
  163. ^ a b Goldsworthy (2003) 73
  164. ^ a b Goldsworthy (2003) 72
  165. ^ Dewijver (1992) 120
  166. ^ a b Goldsworthy (2003) 65–6
  167. ^ Goldsworthy (2000) 165
  168. ^ "Armed Forces - Defence Suppliers Directory - Defence And Security Consultancy - Military Books - Armed Forces of Europe - Royal Navy - British Army - Royal Air Force - RAF - Defence News - Defence Projects". Archived from the original on 19 April 2018. Retrieved 9 May 2018.
  169. ^ Holder (1980) Chapter 2
  170. ^ a b Goldsworthy (2003) 97
  171. ^ Auxiliary unit figures from Holder (2003) 145
  172. ^ Goldsworthy (2000)



  • Arrian Acies contra Alanos (early 2nd century)
  • Dio Cassius Roman History (mid-3rd century)
  • Suetonius De vita Caesarum (early 2nd century)
  • Tacitus Agricola (end of 1st century)
  • Tacitus Annales (end of 1st century)
  • Tacitus Historiae (end of 1st century)
  • Vegetius De re militari (late 4th century)


  • Birley, Anthony (2002). Band of Brothers: Garrison Life at Vindolanda.
  • Burton, G. (1988). The Roman World (J. Wacher ed.).
  • Campbell, Brian (2005). "The Army" in Cambridge Ancient History 2nd Ed Vol XII (The Crisis of Empire 193–337).
  • Davies, R.W. (1988). Service in the Roman Army.
  • Devijver, Hubert (1992). The Equestrian Officers of the Roman Imperial Army.
  • Duncan-Jones, Richard (1990). Structure and Scale in the Roman Economy.
  • Duncan-Jones, Richard (1994). Money and Government in the Roman Empire.
  • Elton, Hugh (1996). Frontiers of the Roman empire.
  • Goldsworthy, Adrian (2000). Roman Warfare.
  • Goldsworthy, Adrian (2003). Complete Roman Army.
  • Grant, Michael (1985). The Roman Emperors.
  • Hassall, Mark (2000). "The Army" in Cambridge Ancient History 2nd Ed Vol XI (The High Empire 70–192).
  • Holder, Paul (1980). Studies in the Auxilia of the Roman Army.
  • Holder, Paul (1982). The Roman Army in Britain.
  • Holder, Paul (2003). Auxiliary Deployment in the Reign of Hadrian.
  • Holder, Paul (2006). Roman Military Diplomas V.
  • Keppie, Lawrence (1996). "The Army and the Navy" in Cambridge Ancient History 2nd Ed Vol X (The Augustan Empire 30BC – 69 AD).
  • Luttwak, Edward (1976). Grand Strategy of the Roman Empire.
  • Mattingly, David (2006). An Imperial Possession: Britain in the Roman Empire.
  • Jones, A.H.M. (1964). The Later Roman Empire.
  • Rossi, L. (1971). Trajan's Column and the Dacian Wars.
  • Roxan, Margaret (2003). Roman Military Diplomas IV.
  • Spaul, John (2000). COHORS2.

External links

Ala (Roman allied military unit)

An Ala (Latin for "wing", plural form: alae) was the term used during the mid- Roman Republic (338-88 BC) to denote a military formation composed of conscripts from the socii, Rome's Italian military allies. A normal consular army during this period consisted of 2 legions, composed of Roman citizens only, and 2 allied alae. Alae were somewhat larger than normal legions (ca. 5,400 v. ca. 4,500 men). From the time of the first Roman emperor, Augustus (ruled 30 BC - AD 14), the term ala was used in the professional imperial army to denote a much smaller (ca. 500), purely cavalry unit of the non-citizen auxilia corps, see Ala (Roman cavalry unit).


The Ampsivarii, sometimes referenced by modern writers as Ampsivari (a simplification not warranted by the sources), were a Germanic tribe mentioned by ancient authors.Their homeland was originally around the middle of the river Ems, which flows into the North Sea, at the Dutch-German border. Most likely they lived between the Bructeri minores (located at the delta of the Yssel) and the Bructerii maiores that were living south of them at the end of the Ems. The name for them is supposed to be a Latin rendering of the Germanic "Ems-werer", meaning "men of the Ems". Reconstruction of the location of other tribes in the area places the Ampsivarii at the lower Ems. In fact at least two modern cities are names after the Ems there: Emden (German) and Emmen (Dutch).


The Attacotti (Atticoti, Attacoti, Atecotti, Atticotti, Atecutti, etc. variously spelled) were a people who despoiled Roman Britain between 364 and 368, along with Scotti, Picts, Saxons, Roman military deserters, and the indigenous Britons themselves. The marauders were defeated by Count Theodosius in 368.

Units of Attacotti are recorded about 400 AD in the Notitia Dignitatum, and one tombstone of a soldier of the Atecutti is known. Their existence as a distinct people is given additional credence by two incidental references to them, as cannibals and as having wives in common, in the writings of Saint Jerome.

Auxilia palatina

Auxilia palatina (sing. auxilium palatinum) were infantry units of the Late Roman army, first raised by Constantine I as part of the new field army he created in about 325.

Some of the senior and probably oldest of these units had special names such as Cornuti or Brachiati; others were named after the tribes from which they were recruited (many of these in eastern Gaul, or among the German barbarians). These units all became palatine units when a distinction was drawn between palatina and the remainder of the comitatenses around 365. There is no direct evidence for the strength of an auxilium, but A.H.M. Jones (History of the Later Roman Empire, Blackwell, Oxford, 1964 p 682) estimates that it may have been 600 or 700. Some auxilia are attested as limitanei, especially on the Danube. It is not clear whether these were regarded as a different category of unit.

Auxillia Mnangagwa

Auxillia Mnangagwa (born 25 March 1963) is a Zimbabwean politician and has served as the First Lady of Zimbabwe since November 2017, as the wife of President Emmerson Mnangagwa. After spending over ten years at the Ministry of Manpower and Development, she joined the Prime Minister's office in 1992. She was elected as a Zanu-PF Member of Parliament in 2015, serving for the same constituency as her husband after he became Vice-President under Robert Mugabe.


The Cornuti ("horned") was an auxilia palatina unit of the Late Roman army, active in the 4th and 5th century. It was probably related to the Cornuti seniores and the Cornuti iuniores.

Heruli (military unit)

The Heruli was an auxilia palatina unit of the Late Roman army, active between the 4th and the 5th century. It was composed of 500 soldiers and was the heir of those ethnic groups that were initially used as auxiliary units of the Roman army and later integrated in the Roman Empire after the Constitutio Antoniniana. Their name was derived from the people of the Heruli. In the sources they are usually recorded together with the Batavi, and it is probable the two units fought together. At the beginning of the 5th century two related units are attested, the Heruli seniores in the West and the Heruli iuniores in the East.

Imperial Roman army

The Imperial Roman army are the terrestrial armed forces deployed by the Roman Empire from about 30 BC to 476 AD. This period is sometimes split into the Principate (30 BC – 284 AD) and Dominate (285–476) periods.

Under Augustus (ruled 30 BC – 14 AD), the army consisted of legions, eventually auxilia and also numeri.

Legions were formations numbering about 5,000 heavy infantry recruited from the ranks of Roman citizens only, transformed from earlier mixed conscript and volunteer soldiers 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.)

Auxilia were organised into regiments of about 500 strong under Augustus, a tenth the size of legions, recruited from the peregrini or non-citizen inhabitants of the empire who constituted approximately 90 percent of the Empire's population in the 1st century AD. The auxilia provided virtually all the army's cavalry, light infantry, archers and other specialists, in addition to heavy infantry equipped in a similar manner to legionaries.

Numeri were allied native (or "barbarian") units from outside the Empire who fought alongside the regular forces 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 protectors of the dominance of the Italian "master-nation", legions enjoyed greater social prestige than the auxilia for much of the Principate. This was reflected in better pay and benefits. In addition, legionaries were equipped with more expensive and protective armour than auxiliaries, notably the lorica segmentata, or laminated-strip armour. However, in 212, the Emperor Caracalla granted Roman citizenship to nearly all the Empire's freeborn 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 25 legions and 250 units of auxiliaries. The numbers grew to a peak of about 450,000 by 211, in 33 legions and about 400 auxiliary units. By then, auxiliaries outnumbered legionaries substantially. From this 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 AD 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. 117–138).

The military chain of command was relatively flat. In each province, the deployed legions' legati (legion commanders, who also controlled the auxiliary units attached to their legion) reported to the legatus Augusti pro praetore (provincial governor), who also headed the civil administration. The governor in turn reported directly to the Emperor in Rome. There was no 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.

Compared to the subsistence-level peasant families from which they mostly originated, legionary rankers enjoyed considerable disposable income, enhanced by periodical 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 the reign of 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 senior warrant officers, were organised in an elaborate hierarchy. Usually promoted from the ranks, they commanded the legion's tactical sub-units of centuriae (about 80 men) and cohorts (about 480 men). They were paid several multiples of basic pay. The most senior centurion, the primus pilus, was automatically elevated to equestrian rank on 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 a soldier's basic pay.

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. 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 military and civil infrastructure. In addition to constructing forts and fortified defences such as Hadrian's Wall, they built roads, bridges, ports, public buildings and entire new cities (colonia), and cleared forests and drained marshes to expand a province's available arable land.

Soldiers, mostly drawn from polytheistic societies, enjoyed wide freedom of worship in the polytheistic Roman system. Only a few cults were banned by the Roman authorities, as being incompatible with the official Roman religion or being 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 cult in the army was Mithraism, an apparently syncretist cult which mainly originated in Asia Minor.


Originally the Latin noun līmes (English: ; Latin pl. līmitēs) had a number of different meanings: a path or balk delimiting fields, a boundary line or marker, any road or path, any channel, such as a stream channel, or any distinction or difference. The term was also commonly used after the 3rd century AD to denote a military district under the command of a dux limitis.Limes has sometimes been adopted in modern times for a border defence or delimiting system of Ancient Rome marking the boundaries and provinces of the Roman Empire, but it was not used by the Romans for the imperial frontier, fortified or not. Some experts suggested that the so-called limes may have been called Munimentum Traiani, Trajan's Bulwark, referring to a passage by Ammianus Marcellinus, according to which emperor Julian had reoccupied this fortification in 360 AD.

List of Roman auxiliary regiments

This article lists auxilia, non-legionary auxiliary regiments of the imperial Roman army, attested in the epigraphic record, by Roman province of deployment during the reign of emperor Hadrian (r. 117–138 CE).

The index of regimental names explains the origin of the names, most of which are based on the names of the subject tribes or cities of the empire where they were originally recruited. (As time went by, they became staffed by recruits from anywhere, especially from the province where they were deployed.)

List of Roman military units that participated in the Marcomannic Wars

This page lists all Roman military units that participated in the Marcomannic Wars. There were thirteen legions, two vexillationes, fifty nine auxiliary units and one naval unit.

Lorica hamata

The lorica hamata is a type of mail armour used by soldiers for over 600 years (3rd century BC to 4th century AD) from the Roman Republic to the Roman Empire. Lorica hamata comes from the Latin hamatus (hooked) from hamus which means "hook", as each ring hooks into one another.

It was issued to both primary legionary and secondary auxilia troops and was mostly manufactured out of bronze or iron. It comprised alternating rows of closed washer-like rings punched from iron sheets and rows of riveted rings made from drawn wire that ran horizontally, producing very flexible, reliable and strong armour. Each ring had an inside diameter of about 5 mm, and an outside diameter of about 7 mm. A standard lorica hamata weighed around 11kg, though this would vary depending on the design and the materials used.

The Romans' knowledge of mail manufacture may have come from 3rd century BC conflicts with the Celts, though the first documented use occurred during the Roman conquest of Hispania. There were several versions of this type of armour, specialized for different military duties such as skirmishers, cavalry and spearmen.

The shoulders of the lorica hamata had flaps that were similar to the Greek linothorax which ran from about mid-back to the front of the torso, and were connected by brass or iron hooks which connected to studs riveted through the ends of the flaps. Up to 30,000 rings went into one lorica hamata, and the estimated production time was two months, even with continual slave labor at the state-run armouries.

Although labor-intensive to manufacture, it is thought that, with good maintenance, the armour could be used for several decades.

Over its lifetime, lorica hamata remained in constant use by legionaries and it was the preferred armour of centurions, who favored its greater coverage and lower maintenance. Constant friction kept the rings of the lorica hamata free of rust, unlike the lorica segmentata, which needed constant maintenance to prevent corrosion.

During the 1st century AD it was starting to be supplemented by lorica segmentata, but had been reintroduced as sole standard-issue armour by the 4th century. The lorica hamata was still common among the legionary soldiers in the 2nd century, despite the use of the more popularly recognized lorica segmentata segmented plate armour. Lorica segmentata was eventually put out of use in the early 4th century for unknown reasons, but lorica hamata remained common for both legionaries and auxiliaries. Later versions had sleeves and covered the legs to the knees.


The Mattiaci were by Tacitus recorded as an ancient Germanic tribe and related to the Chatti, their Germanic neighbors to the east. There is no clear definition of what the tribe's name meant. The Dictionary of Greek and Roman Geography suggests that the name is derived from a combination of 'matte', meaning 'a meadow', and 'ach' (pronounced with the 'ch' as in 'loch'), signifying water or a bath.The Mattiaci were settled on border of the Roman Empire on the right side of the Rhine in the area of present-day Wiesbaden (Aquae Mattiacorum), the southern Taunus, and the Wetterau. Archaeological evidence of Wiesbaden cannot prove their alleged origin. While the worship of various Gaulic deities like Sirona or Epona is attested, there is so far no evidence for Germanic gods nor for specific products of Germanic origin.Tacitus relates that they were not required to pay tribute to the Romans but were to provide assistance in war and thus were an outpost of Roman rule on the border with Germania. He refers to them in his Germania (ch 29) in relation to the Batavians:

[The Batavians] are not under the contempt of paying tribute, nor subject to be squeezed by the farmers of the revenue. Free from all impositions and payments, and only set apart for the purposes of fighting, they are reserved wholly for the wars, in the same manner as a magazine of weapons and armour. Under the same degree of homage are the nation of the Mattiacians. For such is the might and greatness of the Roman People, as to have carried the awe and esteem of their Empire beyond the Rhine and the ancient boundaries. Thus the Mattiacians, living upon the opposite banks, enjoy a settlement and limits of their own; yet in spirit and inclination are attached to us: in other things resembling the Batavians, save that as they still breathe their original air, still possess their primitive soil, they are thence inspired with superior vigour and keenness.

With the Chatti, the Mattaci took part in the Revolt of the Batavi in 69 AD, besieging the Roman city of Mogontiacum (present-day Mainz). After the foundation of the Limes Germanicus, the tribal identity of the Mattiaci seems to have eroded away. When the municipality of the Civitas Mattiacorum had been established unter emperor Trajan, the citizens of Aquae Mattiacorum referred to themselves as vicani Aquaenses instead of "Mattiaci".In the late 1st century AD, Valerius Martialis mentions a kind of soap that was named for the Mattiaci and may have been a local product:

Sapo:Si mutare paras longaevos cana capillos,

Accipe Mattiacas - quo tibi calva? - pilas.Soap:

If you want to change your highly aged hair,

use Pilae Mattiacae - why have a bald head?

A Cohors II Mattiacorum Milliaria Equitata has been attested by several finds in the Roman province of Moesia inferior (e.g. at Sostra). It may have originated in Mattiaci recruited after the Revolt of the Batavi.

The Notitia Dignitatum, an early 5th century document, lists two auxilia palatina, the Mattiaci seniores and the Mattiaci iuniores. The references imply Mattiaci in Roman service.

Numerus (Roman military unit)

A numerus (literally: "number", plural form: numeri) was the term used for a unit of the Roman army.

In the Imperial Roman army (30 BC – 284 AD), it referred to units of barbarian allies who were not integrated into the regular army structure of legions and auxilia. Such units were of undetermined strength and their organisation and equipment probably varied according to the unit's ethnic origin. The term was also applied to quasi-permanent detachments of regular army units.

In the Late Roman army (284–395 AD), a numerus was a regular infantry unit of the limitanei, or border forces, believed to have been c. 300 strong.


Petulantes was an auxilia palatina of the Late Roman army.


The Regii or Reges was an auxilia palatina (light infantry) unit of the Late Roman army, active between the 4th and the 5th century. There was also a legio comitatensis with the same name.

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..


Sequani, in ancient geography, were a Gallic people who occupied the upper river basin of the Arar (Saône), the valley of the Doubs and the Jura Mountains, their territory corresponding to Franche-Comté and part of Burgundy.

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.

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