Latin History

Roman Military

1. The army of the empire - the principate.
The power of the Roman emperors rested on their control of massive armed forces,
paid for out of the emperor's privy purse and bound to him by an oath of personal
allegiance. The vast majority of soldiers were stationed in so called imperial provinces,
commanded by direct appointees of the emperor. The Roman imperial army was thus
in effect very much a private army.

The imperial army was a standing professional army. It contained both conscripts
and volunteers serving a minimum term of sixteen years, though most had to serve
for 25 years or more before they were up for retirement. To preserve the loyalty
of the soldiers on which their position of power rested, the emperors looked well
after their interests. Pay was regular and comparatively generous and on occasion
supplemented by donativa, special bonuses of up to five years pay. On completion
of their term of service soldiers received a large retirement grant of thirteen
to seventeen years' worth of pay. In addition to these monetary rewards serving
soldiers and retired veterans were also granted numerous legal privileges.

The army of the empire was like its republican predecessors made up of a variety
of different units. The most important divisions were however made between the legions,
the auxiliaries, the fleet and the imperial guards. It are these main branches of
the armed services that will be briefly discussed below.

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2. The legions

The organisation

The officers

The non commissioned officers
The core of the Roman army was formed by the units called legions from the latin
legio, meaning a levy. During the first three centuries of the empire the army contained
no more than 25 to 34 legions. Each of these units consisted of about 5000-6000
men recruited among the citizen body. Although the soldiers of the legion were Roman
citizens, this did not imply that they originated from the city of Rome or even
Italy. With the spread of the franchise among the population of the conquered territories
provincials quickly became the most important source of recruits. Italian levies
however remained the most usual source for newly raised legions, although several
units were formed using marines or legionaries detached from existing formations.

The legio was a miniature army that contained within its ranks troops trained and
equipped to perform all kinds of different duties both on and off the battlefield.
Although the vast majority of soldiers served as heavy infantry, other legionaries
fought as cavalry, archers or light infantry. Other specialised troops operated
artillery consisting of torsion guns. The troops were however not solely prepared
for combat. Legionaries regularly served as combat engineers constructing fortifications,
roads and bridges. As the legion counted among its complement a vast number of men
with special skills it was in many ways selfsupporting. A large part of its military
equipment could be produced by artisans in the ranks. Soldiers trained as surveyors,
engineers and architects ensured that the legion needed little outside help for
its building requirements. Administrative duties were performed by other legionaries
both within their unit as well as in the provincial bureaucracy.

Each legion carried a number and a name, e.g. legio X Gemina (the tenth 'twin'
or 'double' legion), to which honorary titles like pia fidelis (dutiful
and loyal) could be added. The numbering and naming of units followed no rationalised
pattern. As many of the formations originated in the various armies of the civil
wars following the death of Iulius Caesar, several legions carried identical numerals
or nicknames. Even new legions that were levied were named and numbered according
to diverse systems. The sense of individuality provided by these numbers and titles
was reinforced by the use of different unit symbols and signs like bulls, boars
or capricorns.

The organisation
The strength and organisation of the legions varied in time and was probably not
completely standardised throughout the army. Generally speaking however the legio
was organised in ten cohortes or cohorts. These cohorts consisted each of three
manipuli, literally 'handfuls', which were in their turn subdivided in two
centuriae or 'hundreds'. These centuriae were composed of a number of contubernia
or 'tentparties'. Although the name centuria would seem to indicate a unit
of a hundred soldiers, this unit could comprise anything from 30 to over 200 individuals.
The usual establishment strength however is thought to have been 80 men. From the
second half of the first century AD in at least some of the legions the first cohort
was reorganised in five double strength centuriae while the remainder continued
to be organised in the old manner.

In addition to the regular organisation of cohortes, manipuli and centuriae of the
legionary heavy infantry there were other subunits for the equites legionis, the
legionary cavalry, and the antesignani or lancearii, the elite legionary light infantry.
The exact details of their organisation are as yet not very clear. For a variety
of duties provisional units known as vexillationes or numeri were formed. The strength
and organisation of these provisional units varied greatly and was only in part
based on the more regular subdivisions of the legion.

The officers
Command of the legion was usually given to a legatus legionis picked by the emperor
from the senatorial class who generally had some previous military experience through
service as a tribunus. In Egypt and from the the start of the third century also
in other provinces the command was not entrusted to a senatorial legatus, but to
a praefectus legionis, an acting commander drawn from the equestrian order. The
legionary commander was assisted by six military tribunes. With the exception of
the units stationed in Egypt one of these tribuni was usually a young senator at
the start of his public career. Known as a tribunus laticlavius from the broad purple
stripes on his tunic this senior tribune was second-in-command. His collegues from
the equestrian order were known as tribuni angusticlavii and generally had done
earlier service as a commander of an auxiliary infantry unit. A former senior centurion
usually performed the duties of praefectus castrorum, camp commandant, and was the
third in the chain of command.

The most important officers in the legions were the centuriones. These men were
partly directly recruited from the Roman knights or the city councilmembers, but
the greater part of the centurions had previously served as soldiers and NCO's
in the legions or the praetorian cohorts. Depending on the organisation of the legion
either sixty or fifty nine centuriones ordinarii commanded the centuriae, while
a varying number of centuriones supernumerarii were employed for special duties.
These officers were known by titles derived from the place of their units in the
old battle order. The hastatus prior, princeps prior and pilus prior were the higher
ranking officers commanding the manipuli. The hastatus posterior, princeps posterior
and pilus posterior acted as their deputies. The cohorts were under the command
of the pilus prior. Distinguished from their fellow officers were the primi ordines,
the senior centurions of the first cohort of the legion. These men had achieved
their posts by prior service in other postings and were chief advisors of the legionary
commanders. The post of primus pilus, the highest ranking centurion in the legion,
carried great prestige and assured entry into the equestrian order.

An uncertain number of supernumerary centurions performed a variety of tasks both
within the legion itself and in other units. Centuriones exercitatores for example
were used as training officers for the legionary cavalry and the horse guards of
provincial governors and the emperor. A centurio stratorum was employed to oversee
the remount system of the provincial armies and on occasion to command the singulares,
the auxiliary soldiers serving as a governor's guard. The centuriones lanceariorum
led the elite legionary infantry known as antesignani or lancearii. Other supernumerary
officers performed duties in the medical service of the legions.

The non commissioned officers
To assist the officers the legion counted a number of NCO's among its strength.
These men were known as principales and depending on their status recieved as duplicarii
double pay or as sesquiplicarii pay and a half. Each centurio ordinarius had an
optio as his deputy. Whereas the centurion led his men from the front, the optio
was stationed at the rear of the unit to keep the legionaries from shirking away
in combat. The signifer or standard bearer carried the signum of the unit. This
standard served both as a rallying point for the soldiers and to communicate simple
visual commands to the troops in battle. The task of carrying the signum in battle
was dangerous as the soldier had to stand in the first rank and could carry only
a small buckler. It may not be strictly coincidental that available epigraphical
evidence contains a relatively large number of discentes signiferorum, trainee standardbearers.
The signifer also assumed responsibility for the financial administration of the
unit and functioned as the legionaries' banker. The tesserarius was a third
NCO attached to a centuria and in charge of the distribution and collection of the
watch words. Both optio and signifer received double pay, but the tesserarius attached
to a centuria was on pay and a half. Other principales like the cornicularius were
attached to the administrative offices of the legion.

A considerable number of legionary soldiers were classed as immunes. These men were
exempted from the more tedious chores because of the special tasks they had to perform,
but received no extra pay. As many a soldier without immunity was forced to bribe
his centurion to escape the less desirable duties, the immunes would in practice
have had some financial gain from their position. Among the immunes were musicians,
military police, cavalry troopers, drill and weapons instructors, artisans, clerks
and medical orderlies. It was usual for both immunes and principales to have served
several years as a munifex, a private liable for all kinds of duty and fatigues,
before they received promotion. Most, if not all, positions were reached after a
period of specialised training as a discens.

Glossary of Roman army terminology

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3. The auxilia

The service conditions
The imperial Roman army continued the republican tradition of supplementing the
citizen legions with units recruited from peregrini, non-citizens from conquered
or allied communities. In the imperial army the total numerical strength of the
various auxiliary formations was roughly comparable to that of the legionary troops.
These forces were known as socii or auxilia and were composed of both regular and
irregular formations. Many modern works distinguish regular auxilia consisting of
cohortes and alae from irregular numeri. This present day division disregards the
fact that irregular units could be designated as a cohors and that numerus was a
very generic term which was also in general use for regular army units. As in the
legiones draftees and volunteers served side by side in the auxiliary forces. With
the spread of Roman citizenship among the population of the conquered territories
the auxilia were increasingly recruiting citizens into the ranks, blurring the original
division between peregrine auxiliaries and citizen legionaries.

The imperial auxilia were composed of a variety of units. Infantry units were generally
organised in cohorts that in the case of cohortes equitatae could include a small
mounted force. Cavalry was usually formed into alae or 'wings'. Both cohortes
and alae could comprise either quingenaria units of approximately 500 man or milliaria
formations of 800-1000 soldiers. Infantry cohorts with a mounted contingent had
an additional 120 to 250 cavalry troopers. Infantry cohorts were composed of three
to five manipuli of each two centuriae. Cavalry alae counted 16 to 24 turmae of
30-40 mounted soldiers. Auxiliary formations were usually commanded by a praefectus
cohortis or praefectus alae, though a tribunus cohortis or legionary centurio was
occasionally employed. Some of these commanders were drawn from the tribal aristocracy,
though most were recruited from the equestrian order. Command of a cavalry alae
was only entrusted to men who had previously served as a praefectus cohortis and
legionary tribunus. The infantry subunits had similar officers and NCO's as
their legionary counterparts. Cavalry turmae were placed under a decurio instead
of a centurion. Legionaries were regularly transferred to act as officers and NCO's
in the units of the auxilia.

Units in the auxiliary forces carried like the legions a number and a title. The
numbering of units followed different patterns and partly reflected the order in
which troops had been levied. The names of units varied greatly, many like cohors
I Batavorum being derived from the tribe that provided the original levies, others
reflecting the armament, e.g. the ala I contariorum, or honouring a former commander,
for example ala Siliana. Redeployment of units and the Roman practice of local recruitment
of replacements meant that the ethnic titles borne by formations did not reflect
the actual origins of its soldiers.

The infantry of the auxilia consisted mainly of soldiers trained and equipped to
fight in a way comparable to that of the legionary heavy infantry. In addition to
these existed specialised formations of light infantry adept at fighting in a looser
order. Units of archers formed a large proportion of the available auxiliary forces.
The alae were for the larger part made up of medium cavalry suited for both skirmishing
and shock tactics. Formations of mounted archers were also much employed. A minority
of the cavalry units were composed of heavy cavalry troopers armed with the contus,
a two handed cavalry spear. These soldiers and some of their mounts as well were
heavily armoured. In at least part of the medium cavalry alae a number of troopers
used to fight as horse archers or heavy cavalry giving the unit a wider range of
combat capabilities.

From the auxiliary units of a provincial army a number of soldiers were selected
for service in the singulares of the governor's guard. Infantrymen from the
cohorts were grouped in the pedites singulares while horsemen from both cohortes
equitatae and alae were brigaded in the equites singulares. Both units were trained
and commanded by legionary centuriones. The strength of these guard formations was
probably related to the numbers of troops deployed in a province. The fact however
that regular army formations like the ala singularium were formed from such elite
units seems to indicate a strength of approximately 500 for both infantry and cavalry
singulares. As promotions in the Roman army were as much depending on personal relations
as on merit, men serving in the governor's guard could look forward to better
army careers.

The service conditions
There is much debate on the actual service conditions enjoyed by soldiers serving
in the auxilia. Recently published evidence seems to indicate that basic pay under
the principate was either 1/6th part less or even equal to that of the legionaries.
Auxiliaries were also included in the occasional distribution of donativa. These
similar service conditions help explain why legionary soldiers were transferring
freely to posts in auxiliary units. An important service condition for non-citizens
enlisted in the auxilia was the grant of Roman citizenship. Generally this was awarded
after 25 years of service, though on occasion grants were made during service as
a reward for bravery in battle. An additional retirement grant of money for the
auxilia is very likely, though the evidence available is ambiguous. The often cited
difference in dimensions of the living space between the larger bases of legions
and the smaller frontier forts may not have served to accentuate status differences
between the legions and auxiliaries. Not only were legionary soldiers regularly
stationed in the smaller forts, but the larger forts were also in part garrisoned
by units of the auxilia.

Glossary of Roman army terminology

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4. The imperial guard

The praetorian guard

The imperial horse guard
The Roman emperor had several guard units at his disposal. The most important of
these were the cohortes praetoriae or praetorian guard. During the reign of the
Julio-Claudian dynasty the Germani custodes corporis or German bodyguard provided
additional security. From the accession of Traianus the equites singulares Augusti
recruited among the auxiliary cavalry formed the emperor's horse guard. The
majority of these men served as guards, i.e. picked troops, rather than bodyguards
directly watching over the person of the emperor. These elite forces at the emperor's
immediate disposal formed the nucleus of the field armies assembled for imperial
military expeditions. Smaller numbers of soldiers were selected among the guard
units for personal protection duties.

The praetorian guard
Under the republic Roman generals had usually formed a guard unit named cohors praetoria
after the praetorium or HQ. Under the empire such units became a privilege reserved
for the emperor under whose auspicia all military operations were conducted. Augustus
originally formed nine numbered cohortes praetoriae consisting of both infantry
and cavalry billeted at Rome and some other Italian cities. This number was later
raised to ten units and the cohorts were concentrated in a large base adjacent to
Rome. Command of the praetorian guard was entrusted to one or two equestrian praefecti
praetorio. Three additional cohortes urbanae with a similar structure were also
present at Rome, but not under the direct control of the praetorian prefects.

A praetorian cohort consisted of approximately 500 infantrymen organised in manipuli
and centuriae and under the overall command of a tribunus. This strength was doubled
in the course of the first century AD. The majority of praetorians fought as heavy
infantry with smaller numbers acting as light infantry lancearii and archers. Added
to these foot soldiers each cohort contained a number of cavalrymen. The combined
equites praetoriani numbered at least 400 men and may even have been a thousand
strong. Other troopers were known as equites speculatores and served as bodyguards
to the emperor. The praetorian cohort that guarded the imperial palace and accompanied
the emperor in the city of Rome was known as the cohors togata. As their duties
were performed within the pomerium, the sacred boundary of the city, these soldiers
could not wear full armour and equipment and therefore dressed in civilian togae,
though keeping their swords at hand.

Service conditions in the praetorian cohorts were better than in the legions. Pay
was substantially higher and donativa were more frequent. The term of service of
sixteen years compared favourably to the 20 to 25 years in the legions. Promotion
opportunities were also excellent. A large part of the legionary posts as centurio
was filled by former praetorian guardsmen. The cohortes praetoriae recruited originally
in Italy and the older coloniae in the provinces, though at times legionaries were
transferred to the guard. From the reign of Septimius Severus the transfer of picked
legionaries became the usual method of filling the ranks of the praetorian guard.

The praetorian guard originally served as the backbone of field armies assembled
for campaigns that involved the emperor, one of his relatives or a praefectus praetorio.
Contrary to popular opinion this meant that the Rome based soldiers had a fair chance
of being involved in combat either against the barbarians from across the borders
or rebellious Roman army units. Despite the increase in the establishment strength
of the praetorian cohorts the guards were increasingly complemented by other formations.
In the course of the third century AD the cohortes praetoriae in the comitatus,
the imperial field army, were regularly supplemented by mobile troops from the legio
II Parthica based at Albanum in Italy. Vexillationes of elite legionaries and auxiliaries
from the frontier armies joining these core formations in the imperial field army
were slowly developing into separate units that were permanently attached to the
imperial retinue.

The imperial horse guard
The citizen guardsmen of the praetorian cohorts had their counterpart in the originally
non-citizen horse guards. These consisted in the Julio-Claudian era of the Germani
custodes corporis disbanded after Nero and the later equites singulares Augusti.
Both these units were also known as Batavi after the tribal origin of many imperial
horse guards. Members were usually recruited from the alae and cohortes equitatae,
though at times men were directly recruited. The centuriones exercitatores or cavalry
training officers for the imperial horse guard were however not drawn from the auxilia,
but were selected from the legionary cavalry. The strength of the horse guard was
approximately a thousand troopers, a number doubled by Septimius Severus. The organisation
of the horse guard resembled that of the cavalry in the auxilia with turmae commanded
by decuriones. An equestrian tribunus functioned as overall commander of the imperial
horse guards.

Glossary of Roman army terminology

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5. The fleet
The main function of the classis or fleet was to combat piracy and to support the
operations of the other armed services. The imperial navy maintained two larger
fleets based in the Mediterranean with smaller squadrons operating on the North
Sea, Black Sea and the major rivers. Ravenna and Misenum were the main naval bases
in the mare nostrum though ships were regularly detached to other ports. There existed
some dedicated fleet installations along the river Rhine and Danube, but most were
attached to bases of the frontier armies. The ships used by the imperial navy comprised
both oared warships and transports as well as sailing craft used mainly for logistical
support.

The vessels of the Roman navy were not manned by the slave rowers of popular imagination.
All personnel serving in the imperial fleet were classed as soldiers, regardless
of their function. Though the fleet had its own marines, these troops were used
for boarding parties rather than amphibious assaults. The status of the sailors
and marines of the Roman navy is somewhat unclear, though the fleet is generally
regarded as the least prestigious branch of service. The fleet recruited freeborn
citizens and peregrini as well as freedmen. Soldiers that did not possess Roman
citizenship received this privilege after a minimum of 25 years of service.

A ship's crew, regardless of its size, was organised as a centuria with one
officer responsible for sailing operations and a centurio for the military tasks.
Among the crew were usually also a number of principales and immunes, some of which
were identical to those of the army and some of which were peculiar to the fleet.
Command of fleets was given to equestrian praefecti, those of the fleets based at
Ravenna and Misenum having the largest prestige. The total strength of the Roman
navy is not known with any exactitude, though it was reportedly some 40.000 strong
during the reign of Diocletian. The Ravenna and Misenum fleets were each at least
numerous enough to furnish the required number of men for a new legio.

Naval forces were used to create both auxiliary units, the cohortes classiariorum
and cohortes classicae, and legionary formations, the legiones I and II Adiutrices.
In addition men were also transferred to the auxilia or legiones on an individual
basis. The fleet squadrons in at least the Danubian provinces may have recieved
direct support from army units, as there is evidence available that a number of
legionary soldiers received training as epibatae or liburnarii for service as marines.