Late Roman Army - Army Structure

Army Structure

The later 4th-century army contained three types of army group: (a) imperial escort armies (comitatus praesentales). These were ordinarily based near the imperial capitals (Milan in the West, Constantinople in the East), but usually accompanied the emperors on campaign. (b) Regional field armies (comitatus). These were based in strategic regions, on or near the frontiers. (c) Border armies (exercitus limitanei).

Types (a) and (b) are both frequently defined as "mobile field armies". This is because, unlike the limitanei units, they were not based in fixed locations. But their strategic role was quite different. The escort armies' primary role was probably to provide the emperor's ultimate insurance against usurpers: the very existence of such a powerful force would deter many potential rivals, and if it did not, the escort army alone was often sufficient to defeat them. Their secondary role was to accompany the emperor on major campaigns such as a foreign war or to repel a large barbarian invasion. The regional comitatus, on the other hand, had the task of supporting the limitanei in operations in the region they were based in.