[13] 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.
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.
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.
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.
[29] 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.
[38] 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.
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.
[60] Most importantly, the eight 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.
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.
[26] 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.
[5] 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).
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.
[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.
[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.
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.
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.
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.
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.
[122] 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 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.
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.
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.
[128] 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.
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.
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.
[95][150] 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.
[155] The remuneration of an auxiliary pedes cohortalis may be compared to a legionary's as follows: Gross salary was subject to deductions for food, clothing, boots and hay (probably for the company mules).
[157] 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.
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.
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..[171] Notes: (1) Table excludes about 2,000 officers (centurions and above).