Manpower

A first issue is the overall size of the late Roman military establishment, since this had always been the largest item of imperial expenditure, and the strains of supporting it were already evident in the Severan period.3 The military problems of the third century occasioned a significant expansion of numbers as imperial frontiers were stabilized during the tetrarchy. Writing in the sixth century, John Lydus recorded the Diocletianic establishment as 389,704 in the armies and 45,562 in the fleets (435,266 in total), and alleged that Constantine doubled Diocletian’s army (de Mensibus 1.27). Slightly later than John Lydus, Agathias offered 645,000 as the total military establishment at an unspecified date, in the context of a rhetorical attack on the depleted Justinianic military forces (5.13.7-8). These figures have to be calibrated against the evidence of the Notitia Dignitatum, a list of the disposition of military units in the eastern and western parts of the empire which was produced in at least two stages in the late fourth and early fifth centuries. This information has occasioned much debate, but the general picture is not implausible, especially once it is realized that a large overall military establishment was required to generate the mobile armies of 20-30,000 attested in the sources. Such an overall increase in size from the Severan period intensified the problems of stable support, straining relations between soldiers and tax-payers, especially when the empire’s overall prosperity was being affected by persistent invasions. Thus the taxation and other economic reforms effected by Diocletian and Constantine were essential elements of the stabilization of the empire’s military position, the foundation for a prolonged period of relative security, almost a century in the West and three centuries in the East.

Roman superiority in manpower had long been recognized as the basis of republican military success (e. g. Polybius 2.24 on the war against Hannibal); in the empire Rome was collectively outnumbered by its enemies, though local superiority could be preserved by restricting the frontiers engaged in active warfare and relying on the empire’s overall demographic prosperity. Until recently the later empire was seen as a period of demographic decline, to be traced back to the plague of the late second century; problems increased as invasions ravaged frontier provinces, harsh taxation drove farmers from their lands, and the increasingly powerful church annexed economic and human resources. The combination of these factors supposedly led to pressure on internal sources of recruits and greater reliance on external barbarian recruitment. Archaeological work over the last generation, especially in the countryside, has changed this picture so that the fourth century is now recognized as a time of demographic strength throughout much of the empire, especially the East; by about 400 the balance had swung in many northern and western provinces, but in Anatolia and the Levant settlement remained dense until the later sixth century when repeated waves of bubonic plague reinforced the effects of protracted warfare.4 Demographic decline, though relevant, no longer offers the easy answer to all late Roman military change, though if weakness in certain areas could not be offset by transfers from elsewhere the sustainability of some armies would be compromised.

A healthy level of population is not sufficient by itself to sustain armies, since men need to be transferred regularly from the civilian to the military sector and might be dissuaded if conditions were wrong. Thus in the second century bc the republic appeared to face a recruitment crisis because it proved difficult to persuade soldiers to present themselves for dangerous and unprofitable service in Spain. In the early empire soldiering was probably seen as a relatively attractive and safe career, and this permitted the empire to replenish its forces through voluntary recruitment rather than conscription. By contrast in the late empire it is believed that conscription was often needed to coerce manpower into the ranks, since the greater dangers of regular fighting on frontiers as well as civil wars increased risks and reduced rewards; legislation attempted to tighten the conscription process, but its repetition merely demonstrates the unpopularity of military service among Romans who came to rely increasingly on non-Roman recruits.5

Book 7 of the Theodosian Code is devoted to military legislation, including one substantial chapter of 22 extracts from laws relating to recruitment. Taken out of context these laws appear to demonstrate that Romans strongly disliked military service: people mutilated themselves or offered slaves to escape conscription, while exemption from the levy was a privilege. However, most of this recruitment legislation is directly linked to specific military crises, periods when heavy losses increased demand but when the clear dangers or loss of enthusiasm or prestige among local recruiters made military service less attractive: the aftermath of Julian’s failed invasion of Persia in 363, the defeat at Adrianople in 378, and the bloody suppression of western usurpations in the late 380s and 390s. Laws on desertion (Cod. Theod. 7.18), another indicator of hostility to military service, show the same distribution. The most urgent legislation was issued by Honorius in the early fifth century as the western court attempted unsuccessfully to squeeze recruits from senatorial estates and drum up volunteers with special incentives. In 406 ten solidi were offered to freeborn recruits, and freedom and a grant of two solidi to slaves (Cod. Theod. 7.13.16-17), with the state resorting to Rome’s extreme manpower solution, employed during the Hannibalic War or after the Varian disaster. This legislation applied across the whole empire, but does not prove that recruitment problems were similarly widespread.

In the late empire membership of a military unit continued to be a considerable asset in terms of dealings with civilians, giving soldiers better status and opportunities to exploit and so attracting citizen recruits: in a settled unit in a reasonably peaceful province, such as that based at Syene in Upper Egypt in the sixth century, there was an entry fee for enrolling in a group which constituted a local elite; hereditary service could be a privilege as well as an obligation. Remuneration could also be significant: in addition to payments in kind and money, there were privileges for veterans including tax relief for their families and immunity from compulsory municipal duties which were the envy of others (Cod. Theod. 7.20.12).6 When weighed against the struggle to eke out a living in a harsh and overcrowded landscape, military service still appeared attractive to the rural populations who constituted the preferred recruits throughout the ancient world: thus two future emperors, Marcian (Evagrius 2.1) and Justin I ( Procopius, Anecdota 6.2), left the rugged central Balkans to seek fortune in Constantinople. The commitment of local elites to channel manpower in the required direction - the secret of the recruitment strength of republican Italy - was also required; an impoverished state with a weak ruler could not command the necessary support.

A system tuned to delivering 30,000 recruits each year from across the whole empire was likely to be put under strain if the requirement suddenly doubled, particularly if much of the extra manpower was to be extracted from a limited number of provinces. Such a crisis might be surmounted, especially if the state’s finances were strong: thus through the fifth century and into the late sixth the East’s wealth stimulated recruitment from recognized areas such as the Balkan highlands, mountainous Isauria in southern Asia Minor, and Armenia. In the West Honorius’ problems are revealed as much by his capitulation to the Senate over the application of conscription to senatorial properties and the admission that the enrolment bonus for free men would not be paid in full until “affairs had been settled” (Cod. Theod. 7.13.12-14; 17) as by the appeal for slaves. In these straitened circumstances different solutions might be necessary, with profound effects on the balance between Roman and non-Roman in the armies.