Part I
From Claudius' invasion in AD43 to Diocletian's accession in 284.
The army comprised two main sections: the legions and the auxiliary units (auxilia). There were around thirty legions distributed among the Empire's provinces – the number wasn't fixed, some legions were lost, others were disbanded or created according to necessity. A legion was divided into ten cohorts, and each cohort was further divided into six centuries. A century was normally made up of eighty men (not a hundred as might be supposed), and each one was divided into ten squads (contubernia) of eight men who would share a tent or barrack-room. It appears, though, that, perhaps from c.70, the First Cohort was arranged differently, having only five centuries, but of double the size (i.e. one hundred and sixty men). A legion was a heavy-infantry unit, but each had a contingent of one hundred and twenty horsemen who functioned as messengers and scouts.
A legion's commanding officer, the legate (legatus legionis), was from the top-rung of Roman society – the senatorial class. He was assisted by six military tribunes, the senior of whom (tribunus laticlavius), would be a young man of senatorial rank getting his first taste of military life. The other five (tribuni angusticlavii) were of the, slightly lower status, equestrian class (sometimes called ‘knights’). The legionaries themselves were Roman citizens, recruited from across the Empire. After around fifteen years service, a man might have achieved the rank of centurion. As the name indicates, a centurion was in charge of a century of men, so (on the basis of the First Cohort having five, double-strength, centuries) there were fifty-nine per legion. The senior centurion of the First Cohort, and hence of the whole legion, was the primus pilus (literally, ‘first javelin’), a post which conferred equestrian status on its holder. He might then become camp prefect (praefectus castrorum), making him third in command of the legion (after the two senatorial officers). Frequently, to avoid removing a whole legion from its post, a detachment – a vexillation (from vexillum, the banner which identified the unit) – would be despatched, possibly with detachments from other legions, to deal with any emergency.
The legions are as renowned for their engineering expertise as they are for their fighting skills. As well as temporary structures built whilst campaigning, they were also responsible for permanent infrastructure projects, such as roads, bridges and fortifications.
A legion (legio) is primarily identified by a number, but, as a result of the somewhat impromptu way legions were created over the years, the number may not be unique – in Britain for instance, there was, for a time, two 2nd Legions. They also have titles, however, and the combination of number and title is exclusive to a particular legion. For most of the first four decades after the invasion of 43, there were four legions garrisoned in Britain. Thereafter, until the 4th century, three legions (some sixteen-and-a-half thousand men) were usually resident. The British legions were:
Legio II Augusta
Created, probably from an earlier legion, by Augustus (27BC–AD14). The only legion known with certainty to have taken part in the invasion. It seems to have remained in Britain for the duration of Roman occupation.
Legio II Adiutrix Pia Fidelis
Formed, in AD69, during the civil war, apparently from the Ravenna fleet. Adiutrix means ‘Helper’. Pia Fidelis given by Vespasian to mark its faithfulness to his cause. In Britain from 71 (probably) until about 87.
Legio VI Victrix Pia Fidelis
Formed by Octavian (who became, the first emperor, Augustus), probably in 41–40BC. Victrix presumably refers to a victory in Spain, where the legion was posted from 30BC to AD69. Pia Fidelis awarded by Domitian in 89. Arrived in Britain in 122 (probably) and still present at the end of the 4th century.
Legio IX Hispana
Origins uncertain, but served in Spain from 30BC until about 19BC – hence its title. Probably part of the invasion army in AD43, although its presence in Britain is not confirmed until 60. Last known to be in Britain in 108. Usually assumed to have departed before 122.
Legio XIV Gemina Martia Victrix
Probably formed by Octavian in 41–40BC. Gemina implies that it was made from the remnants of two legions. Probably part of the invasion army in AD43, although its presence in Britain is not confirmed until 60. Apparently awarded the title Martia Victrix, by Nero, for its role in defeating Boudica. Left Britain in about 67, returned in 69, but left permanently the following year.
Legio XX Valeria Victrix
Formed by Octavian, in 41–40BC or after the battle of Actium (31BC). Probably part of the invasion army in AD43, although its presence in Britain is not confirmed until 60. Probably awarded the title Valeria Victrix from its role in suppressing Boudica's rebellion. Last recorded at the end of the 3rd century – may have been disbanded in the 4th century.
The auxilia were non-citizen units raised from the provinces, and sometimes beyond the Empire's frontiers. Their names reflect the tribe or region where the unit was originally raised. After some time posted ‘abroad’ the unit's regional identity would become diluted as soldiers were replaced with recruits from elsewhere, but the original regional name was retained. As well as infantry, including specialists that the legions did not possess, such as slingers and archers, the auxilia provided the army's cavalry. The infantry was organized into cohorts and the cavalry into wings (alae). Usually the units were, ‘five hundred strong’ (quingenaria), but there were also some units ‘one thousand strong’ (milliaria). A quingenaria infantry cohort was, like a standard legionary cohort, divided into six centuries of eighty men, and this does indeed produce a unit around ‘five hundred strong’. A milliaria infantry cohort, however, had only ten centuries, which falls considerably short of being ‘one thousand strong’. Similarly, a quingenaria cavalry wing comprised sixteen troops (turmae) of thirty-two horsemen, giving a unit size about ‘five hundred strong’, whilst in a milliaria cavalry wing there were only twenty-four troops, so it too falls quite a way short of its advertised strength. There were also auxiliary units where the infantry was supplemented by a small cavalry force: cohortes equitatae. In this case, a quingenaria cohort seems to have comprised the usual six centuries of infantry, but with the addition of four troops of cavalry, hence it exceeded its nominal size. A milliaria cohort, which seemingly consisted of ten centuries of infantry plus eight troops of cavalry, was comfortably ‘one thousand strong’. The horsemen of the cohortes equitatae were apparently not of the same quality as the alae – they were not as well equipped, nor, indeed, as well paid.
As in the legions, each auxiliary century had a centurion. The equivalent rank in the cavalry was a decurion, who was in charge of a troop. After the completion of twenty-five years service, the men were granted, the coveted, Roman citizenship. There are instances of auxiliary units being commanded by tribal chieftains and by legionary centurions, but mostly they were commanded by prefects of equestrian status. The commander of a cavalry wing was a prefect regardless of the unit's size, but a ‘one thousand strong’ cohort was usually commanded by a tribune – in either case, the cohort commander was outranked by the cavalry prefect.
It is evident that more than half of the garrison of Britain was auxiliaries. Auxiliary units are rarely referred to in literary sources, so the evidence for their presence in Britain comes from various types of inscription – including the famous writing tablets from Vindolanda. From the mid-1st century to the beginning of the 3rd century, so-called ‘military diplomas’ – in effect, certificates of citizenship – were given to auxiliary soldiers on their discharge after twenty-five years of service (or sometimes before, in cases of outstanding performance – indeed, it was possible for a whole unit to be rewarded with a grant of citizenship). The diplomas (they actually comprise two engraved bronze plates, about sixteen by thirteen centimetres, wired together), which were copied for the individual retiring soldier from master records kept in Rome, contain a great deal of precise information, for instance:
Photograph courtesy of
the British Museum.
The Emperor Caesar Nerva Trajan Augustus, conqueror of Germany, conqueror of Dacia, son of the deified Nerva, Pontifex Maximus, in his seventh year of Tribunician Power, four times acclaimed Imperator, five times Consul, Father of his Country, has granted to the cavalrymen and infantrymen who are serving in four wings and eleven cohorts called: 1st Thracian and 1st Pannonian Tampiana and Sebosius' Gauls and Vettonian Spaniards, Roman Citizens; and 1st Spanish and 1st Vangiones one thousand strong and 1st Alpine and 1st Morini and 1st Cugerini and 1st Baetasii and 1st Tungrians one thousand strong and 2nd Thracians and 3rd Bracari and 3rd Lingones and 4th Dalmatians, who are stationed in Britain under Lucius Neratius Marcellus, who have served twenty-five or more years, whose names are written below, citizenship for themselves, their children and descendants, and the right of legal marriage with the wives they had when citizenship was granted to them, or, if any were unmarried, with those they later marry, but only a single one each.
19 January, in the consulships of Manius Laberius Maximus and Quintus Glitius Atilius Agricola, both for the second time [i.e. AD103].
To Reburrus, son of Severus, from Spain, decurion of 1st Wing of Pannonians Tampiana, commanded by Gaius Valerius Celsus.
Copied and checked from the bronze tablet set up at Rome on the wall behind the temple of the deified Augustus, near [the statue of] Minerva.
[Witnessed by] Quintus Pompeius Homerus; Gaius Papius Eusebes; Titus Flavius Secundus; Publius Caulius Vitalis; Gaius Vettienus Modestus; Publius Atinius Hedonicus; Tiberius Claudius Menander.
The above diploma was found near Malpas, Cheshire. Clearly its recipient, the decurion Reburrus, settled in Britain after his discharge from the army. Others, though, chose to return home. One such was Gemellus, son of Breucus, who was discharged on 17th July 122. It just so happens that Gemellus had served in the same unit as Reburrus – 1st Wing of Pannonians Tampiana (Ala I Pannoniorum Tampiana) – though, of course, nineteen years later. Unlike Reburrus, though, Gemellus actually was from Pannonia. His diploma was found at Brigetio in Pannonia (now Szőny, in Hungary), and it names thirteen cavalry wings and thirty-seven cohorts (the greatest number of units recorded by any diploma – representing a force some twenty-five thousand strong), that had men receiving citizenship in Britain on the same date.
There was, in fact, no ban on citizens joining the auxiliaries, and, as time progressed and the number of citizens grew, that particular distinction between legions and auxiliary units faded. It disappeared completely when, in 212, Caracalla (by what is known as the Constitutio Antoniana) conferred Roman citizenship on all of the Empire's free people. Caracalla's father, Septimius Severus, had, in the mid 190s, created three new legions. Each had an equestrian, rather than a senatorial commander. In the 260s, Gallienus excluded men of senatorial rank from military command. The Empire's frontiers came under unprecedented pressure during, what is known as the ‘Third-Century Crisis’ of 235–284. In order to increase the army's ability to mount a rapid response over a wide area, greater emphasis was placed on the cavalry, and splitting legions into vexillations became the norm.
Part II
From Diocletian's accession, in AD284, onwards.
The structure of the Late Roman army was the result of reforms instituted by Constantine (306–337), which built on the reforms of Diocletian (284–305), which, in turn, built on lessons learned during the ‘Third-Century Crisis’. The upshot of this evolutionary process was that the army was divided into two main elements: the comitatenses (mobile field-armies) and the limitanei (frontier troops). (The term limitanei is first attested in 363: ‘Theodosian Code’ XII.1.56.) The commander of the frontier forces in a particular region, which could range over more than a single province, had the title dux (duke) or sometimes, rather grander, comes (count). Cavalry units of the comitatenses were commanded by the magister equitum, infantry units by the magister peditum. When sections of a field-army operated independently they were commanded by a comes.
The ‘Notitia Dignitatum’ (Register of Dignitaries) is a list of Roman civil and military posts, originating from round about 400 – as far as the information concerning Britain is concerned, it probably dates from c.395, with some slightly later modifications. The limitanei of Roman Britain are listed under the command of two officers: the dux Britanniarum (Duke of the Britains) and the comes litoris Saxonici (Count of the Saxon Shore).
The command of the dux Britanniarum depicted in a copy of the ‘Notitia Dignitatum’ made in 1436 (Oxford, Bodleian Library MS Canon. Misc. 378). No surviving manuscript of the ‘Notitia’ is earlier than the 15th century, and all extant copies are believed to derive from a single, c.10th century, copy (which was apparently lost in the late-16th century).
Under the dux Britanniarum are thirty-seven units dotted about, what is now, northern England and along Hadrian's Wall. The first fourteen garrison sites – appearing before those categorized as “along the line of the wall” – feature in an illustration representing his command (right). Not all place names given by the ‘Notitia’ can be equated to known sites. On the other hand, there are more forts that archaeology shows were occupied than are recorded by the ‘Notitia’. The first unit in the list is the 6th Legion (Legio VI Victrix Pia Fidelis). (The Empire now had many more legions, but they were of much smaller size – perhaps a thousand men. Old legions were, apparently, permanently divided into separate units.) The location of the 6th is not actually named by the ‘Notitia’, but presumably it was York (which had been the legion's base since c.122). The dux Britanniarum himself may well have been based at York also.
The comes litoris Saxonici has command over the, so-called, ‘Saxon Shore Forts’ – nine forts ranged round the south-east coastline. Why this particular officer had the elevated title of comes is not obvious – perhaps the command originally included the Gallic as well as the British side of the Channel. The unit occupying the fort at Richborough is named as Legio II Augusta. Richborough is only a fraction of the size of the legion's erstwhile fortress at Caerleon, so the unit was clearly much smaller.
The visualization (Oxford, Bodleian Library MS Canon. Misc. 378) of the comes Britanniarum (or comes Britaniae as he appears in the heading) features a walled town.
The third of the old British legions, Legio XX Valeria Victrix, does not appear in the ‘Notitia’. It is last attested on coins issued by the usurper Carausius (286–293, see: New Empires), and it may well have been disbanded and dispersed into other units in the intervening period. The legion's old fortress, at Chester, does not appear either. Neither does II Augusta's at Caerleon, in modern South Wales. In fact, the area that is now Wales does not figure in the ‘Notitia’ at all. Archaeological evidence tends to support the notion that Roman troops had been withdrawn from Wales, and from Chester, by Magnus Maximus in the 380s (see: Ruin).
The ‘Notitia’ places a force of the comitatenses, a small mobile field-army, in Britain. The nine units listed are commanded by the comes Britanniarum (Count of the Britains). One of the units, called the Secundani Iuniores, may have been created from a vexillation of the old-style Legio II Augusta. It seems that the comitatenses were usually billeted in towns, rather than being stationed in forts. Where the British field-army units were is not known. Neither is it known when the field-army was established in Britain. It would not appear to have existed in 367, when Theodosius had to bring across field-army units from the Continent (see: A Barbarian Conspiracy), and it is frequently suggested that it was a creation of Stilicho, in the late-390s.