Editing Roman army (section)

== Imperial Roman army (30 BC – AD 284) ==
{{main|Imperial Roman army}}
Under the founder–emperor [[Augustus]] (ruled 30&nbsp;BC – 14&nbsp;AD), the [[Roman legion|legions]], c. 5,000-strong all-heavy infantry formations recruited from [[Roman citizenship|Roman citizens]] only, were transformed from a mixed conscript and volunteer corps serving an average of 10 years, to all-volunteer units of long-term professionals serving a standard 25-year term (conscription was only decreed in emergencies). In the later 1st century, the size of a legion's First Cohort was doubled, increasing legionary personnel to c. 5,500.

[[File:Engineering corps traian s column river crossing.jpg|thumb|left|Roman auxiliary infantry crossing a river. They can be distinguished by the oval shield (''[[clipeus]]'') they were equipped with, in contrast to the rectangular ''[[Scutum (shield)|scutum]]'' carried by legionaries. Panel from [[Trajan's Column]], Rome]]
Alongside the legions, Augustus established the [[auxilia]], a regular corps of similar numbers to the legions, recruited from the ''[[Peregrinus (Roman)|peregrini]]'' (non-citizen inhabitants of the empire&nbsp;– about 90% of the empire's population in the 1st century). As well as comprising large numbers of extra heavy infantry equipped in a similar manner to legionaries, the auxilia provided virtually all the army's cavalry (heavy and light), light infantry, archers and other [[Immunes|specialists]]. The auxilia were organised in c. 500-strong units called {{Lang|la|cohortes}} (all-infantry), {{Lang|la|alae}} (all-cavalry) and {{Lang|la|cohortes equitatae}} (infantry with a cavalry contingent attached). Around 80 AD, a minority of auxiliary regiments were doubled in size. Until about 68 AD, the auxilia were recruited by a mix of conscription and voluntary enlistment. After that time, the auxilia became largely a volunteer corps, with conscription resorted to only in emergencies. Auxiliaries were required to serve a minimum of 25 years, although many served for longer periods. On completion of their minimum term, auxiliaries were awarded Roman citizenship, which carried important legal, fiscal and social advantages. Alongside the regular forces, the army of the [[Principate]] employed allied native units (called ''[[Numerus (Roman military unit)|numeri]]'') from outside the empire on a mercenary basis. These were led by their own aristocrats and equipped in traditional fashion. Numbers fluctuated according to circumstances and are largely unknown.

As all-citizen formations, and symbolic guarantors of the dominance of the Italian hegemony,{{citation needed|date=September 2018}} legions enjoyed greater social prestige than the auxilia. This was reflected in better pay and benefits. In addition, legionaries were equipped with more expensive and protective armour than auxiliaries. However, in 212, the emperor [[Caracalla]] granted Roman citizenship to all the empire's inhabitants. At this point, the distinction between legions and auxilia became moot, the latter becoming all-citizen units also. The change was reflected in the disappearance, during the 3rd century, of legionaries' special equipment, and the progressive break-up of legions into cohort-sized units like the auxilia.

[[File:MBALyon2018 - Expo Claude - Relief Pretoriens - cropped foreground.jpg|thumb|upright|Roman relief fragment depicting the [[Praetorian Guard]], c. 50 AD]]
By the end of Augustus' reign, the imperial army numbered some 250,000 men, equally split between legionaries and auxiliaries (25 legions and c. 250 auxiliary regiments). The numbers grew to a peak of about 450,000 by 211 (33 legions and c. 400 auxiliary regiments). By then, auxiliaries outnumbered legionaries substantially. From the peak, numbers probably underwent a steep decline by 270 due to plague and losses during multiple major barbarian invasions. Numbers were restored to their early 2nd-century level of c. 400,000 (but probably not to their 211 peak) under [[Diocletian]] (r. 284–305). After the empire's borders became settled (on the [[Rhine]]-[[Danube]] line in Europe) by 68, virtually all military units (except the [[Praetorian Guard]]) were stationed on or near the borders, in roughly 17 of the 42 [[Roman province|provinces]] of the empire in the reign of [[Hadrian]] (r. 117–138).

The military chain of command was relatively uniform across the Empire. In each province, the deployed legions' ''[[Legatus|legati]]'' (legion commanders, who also controlled the auxiliary regiments attached to their legion) reported to the {{Lang|la|[[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 [[Staff (military)|army general staff]] in Rome, but the leading ''[[praefectus praetorio]]'' (commander of the [[Praetorian Guard]]) often acted as the emperor's de facto military chief-of-staff.

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

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

[[File:Colonne trajane 1-43 (cropped).jpg|thumb|left|Relief scene of Roman legionaries building a road, from [[Trajan's Column]], [[Museum of Roman Civilization]], Rome]]
Soldiers spent only a fraction of their lives on campaign. Most of their time was spent on routine military duties such as training, patrolling, and maintenance of equipment, etc. Soldiers also played an important role outside the military sphere. They performed the function of a provincial governor's police force. As a large, disciplined and skilled force of fit men, they played a crucial role in the construction of a province's Roman military and civil infrastructure: in addition to constructing forts and fortified defences such as [[Hadrian's Wall]], they built roads, bridges, ports, public buildings, entire new cities (Roman colonies), and also engaged in large-scale forest clearance and marsh drainage to expand the province's available arable land.

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