Roman Army - Late Roman Army/East Roman Army (284–641)

Late Roman Army/East Roman Army (284–641)

The Late Roman army is the term used to denote the military forces of the Roman Empire from the accession of Emperor Diocletian in 284 until the Empire's definitive division into Eastern and Western halves in 395. A few decades afterwards, the Western army disintegrated as the Western empire collapsed. The East Roman army, on the other hand, continued intact and essentially unchanged until its reorganization by themes and transformation into the Byzantine army in the 7th century. The term "late Roman army" is often used to include the East Roman army.

The army of the Principate underwent a significant transformation as a result of the chaotic 3rd century. Unlike the Principate army, the army of the 4th century was heavily dependent on conscription and its soldiers were more poorly remunerated than in the 2nd century. Barbarians from outside the empire probably supplied a much larger proportion of the late army's recruits than in the army of the 1st and 2nd centuries.

The size of the 4th-century army is controversial. More dated scholars (e.g. A.H.M. Jones, writing in the 1960s) estimated the late army as much larger than the Principate army, half the size again or even as much as twice the size. With the benefit of archaeological discoveries of recent decades, many contemporary historians view the late army as no larger than its predecessor: under Diocletian c. 390,000 (the same as under Hadrian almost 2 centuries earlier) and under Constantine no greater, and probably somewhat smaller, than the Principate peak of c. 440,000. The main change in structure was the establishment of large armies that accompanied the emperors (comitatus praesentales) and were generally based away from the frontiers. Their primary function was to deter usurpations. The legions were split up into smaller units comparable in size to the auxiliary regiments of the Principate. In parallel, legionary armour and equipment were abandoned in favour of auxiliary equipment. Infantry adopted the more protective equipment of the Principate cavalry.

The role of cavalry in the late army does not appear to have been enhanced as compared with the army of the Principate. The evidence is that cavalry was much the same proportion of overall army numbers as in the 2nd century and that its tactical role and prestige remained similar. Indeed, the cavalry acquired a reputation for incompetence and cowardice for their role in three major battles in mid-4th century. In contrast, the infantry retained its traditional reputation for excellence.

The 3rd and 4th centuries saw the upgrading of many existing border forts to make them more defensible, as well as the construction of new forts with much higher defensive specifications. The interpretation of this trend has fuelled an ongoing debate whether the army adopted a defence-in-depth strategy or continued the same posture of "forward defence" as in the early Principate. Many elements of the late army's defence posture were similar to those associated with forward defence, such as a loser forward location of forts, frequent cross-border operations, and external buffer-zones of allied barbarian tribes. Whatever the defence strategy, it was apparently less successful in preventing barbarian incursions than in the 1st and 2nd centuries. This may have been due to heavier barbarian pressure, and/or to the practice of keeping large armies of the best troops in the interior, depriving the border forces of sufficient support.