Where was the Roman Army in AD408?

[Nathan Ross]

Germanics in Roman units were basically Roman soldiers and indistinguishable.

And vice versa, perhaps?

I'm rather new to this area of Roman history, and I've probably been looking at the events of the early 5th century through the lens of the early-mid 4th; I should certainly read Burns more closely, for starters!

I did listen to a few episodes of Patrick Wyman's Fall of Rome Podcast over the weekend, though, which was very interesting - at one point Wyman suggests (following Burns, and Guy Halsall, I think) that, by the closing decades of the 4th century, 'barbarians' and 'Roman soldiers' had become almost indistinguishable, at least in the eyes of most Roman civilians: 'the Goths' were less a tribe or ethnicity than a Romano-Germanic military caste, most of whose members had been living within the empire for a generation or more.

This seems quite a persuasive view - and would explain why the bulk of the Italian field army was unable or unwilling to counter Alaric's invasion - but it does return to the initial question: if the Roman army in Italy in 408 was mainly (or 'entirely'?) composed of barbarian recruits, how did Olympius and others manage to turn the troops at Ticinum against Stilicho and his allies (and, by extension, his 'pro-barbarian' policies)? Who was it who massacred the wives and families of the Gothic federate troops in Italy, if the regular army was mainly 'barbarian'? Was this just a matter of one group of Romanised-barbarised-Romano-barbarians (!) being pitted against another?

And where, in all this, does a figure like Constantius III appear? He was apparently a Roman, from Naissus, and seems to have risen from the ranks of the army. How many other men like him were there serving in the army of the day? Would it still be possible for anybody to distinguish between 'Romans' and 'non-Romans' within the military ranks, and perhaps exploit the differences, or would this have been a meaningless distinction by the end of the 4th century?