The army of the later Empire has had a bad press, being widely regarded as a motley collection of half trained , poorly equipped, incompetent peasant farmers associated with increasing numbers of Germanic barbarians whose very presence diluted and degraded the once proud Roman military machine.

This was an army that, even with its vastly increased numbers, proved ultimately incapable of preventing the destruction of the Empire, so it clearly cannot have been anywhere near as effective as its early Imperial counterpart, or so the theory runs.

In any case, the later Empire was, as Gibbon saw it, a period  of decline and fall, and the army must surely have shared in the general degeneration of Roman life and society.

Actually, this is to misunderstand both the nature and ethos of the later army and that of the society of which it formed a part. The fourth century world may have been very different from that of the Julio-Claudians but that difference does not necessarily imply decline. Such moral judgements seem inappropriate. First century society was not intrinsically 'better' than fourth century society (one only has to think of Britain's fourth century villas and their mosaics) and the later Roman army was just as effective in pursuing the defensive goals for which it was designed as its earlier counterpart was in fulfilling Rome's expansionist mission.

In fact, the main reason for the evolution of the later military system was precisely because the early Imperial army had proved incapable of dealing with the changed conditions and the new threats to the Empire which emerged during the later second and third centuries. Had the system not adapted to change, the Empire would undoubtedly have collapsed considerably earlier than it actually did.

Obviously the later army  doesn't seem to compare very favourably with the expansionist force of earlier days since by its very nature it was a defensive army and defensive armies do not seem to hold much glamour. In addition, in appearance there is no doubting that it seems to have more in common with the Bayeux tapestry than with Trajan's column and one cannot argue with the fact that this has much to do with the increasing proportion of 'barbarian' troops serving Rome in the fourth century.

Yet appearances can be deceptive:

• A defensive army is not necessarily incompetent or weak - how expansionist is the British army today?

• Developing  'barbarisation' does not necessarily imply a decline in standards - even the much derided frontier troops or 'limitanei' were capable of putting up stiff resistance  when the occasion arose, the commissariat was still able to organise the provision of military supplies on a colossal scale while so-called barbarian troops proved disciplined, skilled and conspicuously loyal in their service to the Roman state.
  

• In fact, the recruitment of soldiers from beyond the frontiers was only the culmination of a long-standing Roman tradition of employing the fighting skills of others to their advantage and it is hard to see where sufficient fighting men of the right quality could have been obtained in an Empire which by this time may well have lost much of its fighting edge thanks to its success in spreading the benefits of civilisation and which may well have been experiencing demographic problems. In any case, they did not become preponderant until the very end of the fourth century.
  

• Lack of body armour may make later Roman troops appear 'primitive' next to their earlier counterparts, but this only represents the normal fighting kit of troops from beyond the frontiers which then spread to those recruited from within the Empire. This does not mean that the later Empire was somehow in terminal technological decline - artillery was still very much in use at this time, while heavily armoured cavalry, the cataphracti and clibanarii , were employed in field armies throughout the Roman world and testified to the continuing skill of Roman armourers.