Legionary Officers and NCOs - Late Roman Army (284 - 565 AD)

[ValentinianVictrix]

So if Vegetius did see unarmored infantry, that was nothing new.

I agree. Plus, the lines where Vegetius describes the lack of armour are not from an observation, but he claims to describe a formar process in which the soldiers appealed to the emperor to get permission not to wear armour:

Vegetius (1.20.3): But negligence and sloth having by degrees introduced a total relaxation of discipline, the soldiers began to think their armor too heavy, as they seldom put it on. They first requested leave from the Emperor to lay aside the cuirass and afterwards the helmet. In consequence of this, our troops in their engagements with the Goths were often overwhelmed with their showers of arrows. Nor was the necessity of obliging the infantry to resume their cuirasses and helmets discovered, notwithstanding such repeated defeats, which brought on the destruction of so many great cities.

Especially the second part sound like fantasy to me.

I dont think we can entirely dismiss Vegetius out of hand. The Emperor that the appeal was made to was Gratian. He was Emperor of the West at the time of Valen's death and he himself may well have been murdered by his own troops after causing ill-feeling by surrounding himself with Alan's as his bodyguard. These may have acted both as mounted and foot warriors. Only their nobles were noted as wearing body armour. Plus, Gothic infantry in the main did not wear armour and when initially recruited into the Roman army at that time probably fought in their native styles until they were trained and equiped otherwise. It may well be the case that as more and more Goth's, Huns and Alan's began to be recruited there was less of a need to protect them as well as 'native' Romans, after all there appeared to be a never-ending supply of willing barbarian recruits, and who cared if they got stuck full of arrows?