As an aside, I've read the Late Roman "barbarisation" of the army wasn't really very literal - most of the recruits still came from within the Empire - but rather cultural. The military had became uncoupled from the civilian life already when the old militia system withered; in the centuries afterward it had quite enough time to develop a culture entirely of its own, and if I've understood correctly that took to consciously affecting "barbarian" (or in any case, what Roman stereotypes regarded as "barbarian") customs, modes of dress, fashions etc. to further distinguish itself as "a world apart" - and of course also due to the associations such paraphenelia had with the toughness, ferocity etc. the Romans regarded as characteristical of the "barbarians".