Military of Ancient Rome - Personnel

Personnel

See also: Structural history of the Roman military

At its territorial height, the Roman Empire may have contained between 45 million and 120 million people. Historian Edward Gibbon estimated that the size of the Roman army "most probably formed a standing force of 3,750,000" men at the Empire's territorial peak in the time of the Roman Emperor Hadrian. This estimate probably included only legionary and auxiliary troops of the Roman army. However, Gibbon states that it is "not... easy to define the size of the Roman military with any tolerable accuracy." In the late Imperial period, when vast numbers of foederati were employed by the Romans, Antonio Santosuosso estimated the combined number of men in arms of the two Roman empires numbered closer to 700,000 in total (not all members of a standing army), drawing on data from the Notitia Dignitatum. However, he notes that these figures were probably subject to inflation due to the practice of leaving dead soldiers "on the books" in order to continue to draw their wage and ration. Furthermore, it is irrespective of whether the troops were raised by the Romans or simply hired by them to fight on their behalf.

There is no archaeological evidence that suggests that women constituted a significant proportion of troops even amongst the federated troops of the late empire. For the majority of its history, the Roman army was open to male recruits only, and for a greater part of that history only those classified as Roman citizens (as opposed to allies, provincials, freedmen and slaves) were eligible for military service as legionaries, though a great deal of non-citizens could join as auxiliaries, and perhaps earn citizenship in return.

Initially, Rome's military consisted of an annual citizen levy performing military service as part of their duty to the state. During this period, the Roman army would prosecute seasonal campaigns against largely local adversaries. As the extent of the territories falling under Roman suzerainty expanded, and the size of the city's forces increased, the soldiery of ancient Rome became increasingly professional and salaried. As a consequence, military service at the lower (non-staff) levels became progressively longer-term. Roman military units of the period were largely homogeneous and highly regulated. The army consisted of units of citizen infantry known as legions (Latin: legiones) as well as non-legionary allied troops known as auxilia. The latter were most commonly called upon to provide light infantry or cavalry support.

Military service in the later empire continued to be salaried and professional for Rome's regular troops. However, the trend of employing allied or mercenary troops was expanded such that these troops came to represent a substantial proportion of Rome's forces. At the same time, the uniformity of structure found in Rome's earlier military forces disappeared. Soldiery of the era ranged from lightly armed mounted archers to heavy infantry, in regiments of varying size and quality. This was accompanied by a trend in the late empire of an increasing predominance of cavalry rather than infantry troops, as well as a requital of more mobile operations.