26 - The army at the height of the Empire.

The army at the height of the Empire.  Imperial legions and reformation of the auxilia (27 BC – 117 AD).  By the turn of the millennium, Emperor Augustus' primary military concern was to prevent Roman generals from further usurping the imperial throne. The experience of Caesar and, earlier, Marius and Sulla, had demonstrated the willingness of "emergency" (re-activated previously decommissioned) legions containing troops keen for plunder to follow their generals against the state. Augustus therefore removed the need for such emergency armies by increasing the size of the standing armies to a size sufficient to provide territorial defence on their own. Perhaps due to similar concerns, the legions and auxiliaries of the army were supplemented under the Emperor Augustus by an elite formation of guards dedicated to the protection of the Emperor. The first such unit was based in Rome and were known as the Praetorian Guard, and a second similar formation were known as the Cohortes urbanae.  The legions, which had been a mix of life professionals and civilian campaigners, was altered into a standing army of professionals only. The actual structure of the cohort army remained much the same as in the late Republic, although around the 1st century AD the first cohort of each legion was increased in size to a total of 800 soldiers. However, while the structure of the legions remained much the same, their make-up gradually changed. Whereas early Republican legions had been raised by a draft from eligible Roman citizens, imperial legions were recruited solely on a voluntary basis and from a much wider base of manpower. Likewise, whereas Republican legions had been recruited almost exclusively in Italy, early Imperial legions drew most of their recruits from Roman colonies in the provinces from 68 AD onwards. One estimate place the proportion of Italian troops at 65% under Augustus in c. 1 AD, falling to around 49% by the end of Nero's reign.  Since the legions were officially open only to Roman citizens, Max Cary and Howard Hayes Scullard argue that at least in some provinces at this time "many provincials must have been recruited who lacked any genuine claim to Roman citizenship but received it unofficially on enlistment," a practice that was to increase in the 2nd century. This is most likely in those provinces where the pool of Roman citizens was not large enough to fulfil the provincial army's recruitment needs. One possible example is Britain, where one estimate puts the citizen pool in the 1st century at only 50,000 out of a total provincial population of around two million.  At the same time as the legions underwent these transformations, the auxilia were reorganized and a number of allied troops were formalised into standing units similar to legions. Rather than being raised re-actively when required, the process of raising auxiliary troops was carried out in advance of conflicts according to annual targets. Whereas the internal organisation of the auxilia had previously been left up to their commanders, in the early empire they were organised into standardised units known as turmae (for cavalry alae) and centuriae (for infantry cohortes). Although never becoming as standardised in their equipment as the legions, and often retaining some national flavour, the size of the units at least was standardised to some degree. Cavalry were formed into either an ala quingenaria of 512 horsemen, or an ala millaria of 1,000 horsemen. Likewise, infantry auxilia could be formed into a cohors quingenaria of 500 men or a cohors millaria of 1,000 men. Mixed cavalry/infantry auxiliaries were typically formed with a larger proportion of foot than horse troops: the cohors equitata quingenaria consisted of 380 foot and 120 horsemen, and the cohors equitata millaria consisted of 760 foot and 240 horsemen.   The vitality of the empire at this point was such that the use of native auxilia in the Roman army did not apparently barbarise the military as some scholars claim was to happen in the late empire. On the contrary, those serving in the auxilia during this period frequently strove to Romanise themselves. They were granted Roman citizenship on retirement, granting them several social advantages, and their sons became eligible for service in the legions.  As with the army, many non-Italians were recruited into the Roman Navy, partly because the Romans had never readily taken to the sea. It appears that the navy was considered to be slightly less prestigious than the auxilia but, like the auxilia, troops could gain citizenship on discharge upon retirement. In terms of structure, each ship was staffed by a group of men approximately equivalent to a century, with ten ships forming a naval squadron.  Introduction of vexillationes (76–117 AD).  Through the final years of the 1st century AD, the legions remained the backbone of the Roman army, although the auxilia in fact outnumbered them by up to half as much again. Within the legions, the proportion of troops recruited from within Italy fell gradually after 70 AD. By the close of the 1st century, this proportion had fallen to as low as 22 percent, with the remainder drawn from conquered provinces. Since technically only citizens were allowed to enlist in the legions, where recruits did not possess citizenship then, at least in some instances, citizenship "was simply given [to] them on enlistment". During this time, the borders of the Empire had remained relatively fixed to the extent originally reached under the Emperor Trajan. Because of this, the army was increasingly responsible for protecting existing frontiers rather than expanding into foreign territory, the latter of which had characterised the army's earlier existence. As a result, legions became stationed in largely fixed locations. Although entire legions were occasionally transferred into theatres of war, they remained largely rooted in one or more legionary bases in a province, detaching into smaller bodies of troops (Latin: vexillationes) on demand. This policy eventually led to a split of the military's land-based forces into mobile and fixed troops in the later Empire. In general, the best troops were dispatched as vexillationes, and the remainder left to guard border defenses were of lower quality, perhaps those with injuries or near retirement. Wikipedia: Text is available under the Creative Commons Attribution-ShareAlike 4.0 License.This episode includes AI-generated content.