Unit sizes in the Late Roman army

Coello, Terence Arnold (1995). Unit sizes in the Late Roman army. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000e05e

Abstract

It is generally argued that units of the Late Roman Army were substantially smaller than those of the Early Empire. This concept may be largely accurate but a number of problems are involved and generalisations must be made with caution.

Even for the Principate unit sizes are not easy to establish, although it seems likely that legions contained about 5,000 men each, and auxiliary units approximately their nominal quingenary or milliary strengths. Documentary evidence is limited but does tend to confirm the statements of ancient writers - about quingenary equitate cohorts, for example. The significant increase in the total of units during the fourth century provides powerful if inferential evidence for smaller units: this can be approximately quantified from the lists of the NoMa. Literary evidence for the Late Empire is contradictory: there are indications of small units but also references to larger ones. This may well reflect a reality of a majority of smaller units co-existing with some survivals of traditional ones

The payments in cash and kind recorded in the Panopolis papyri have been used to extrapolate sizes for units in Diocletianic Egypt. Some units - especially cavalry - may have been quite under-strength relative to Principate norms but too many uncertainties surround the calculations involved to allow confidence in the estimates, even if they had a wider relevance.

Archaeology provides evidence for small units, although these are not always easy to calculate precisely. The drastic reductions implied by some excavations need to be treated with caution: it is not clear, for example, that the north British "chalets" do actually represent married quarters for tiny garrisons.

A number of other factors need to be considered, such as the extent of the internal re-organisation of units, and of the practice of official records including "ghost' soldiers.