Roman helmets: Imperial Gallic/Italic and Ridge - comparisons and sources

[Nathan Ross]

lorica segmentata has been abandoned... less protection.

Why would mail offer less protection? Mail was used for over a thousand years, all across the world. If segmentata was superior, why was it never used again by anyone else after the Romans abandoned it?

It is quite clear that the army organization was decreasing overall.

This is not at all 'clear'. As I say, the Notitia Dignitatum of cAD400 suggests a highly organised military structure.

Centralization is not a good thing, if you lose the ability to operate in the field.

The later Roman army did not 'lose the ability to operate in the field' - until Adrianople (and after it, for the most part) they experienced very few defeats and were highly effective. The record of victory of the tetrarchic army of AD290-305, for example, against all enemies and on fronts, is probably unsurpassed.

We might ask whether, faced with the military demands of the 3rd and 4th centuries, the army and state structures of Trajan or Marcus Aurelius would have fared as well.

you are on the downhill section.

Only with the benefit of centuries of historical hindsight was the empire of Constantine or even Valentinian 'on the downhill section'

We should remember that the eastern Roman empire survived and prospered for hundreds of years after the fall of the west - using the same military equipment!

And this is a reflection of the social crisis that the empire was experiencing.

At what time, and in what way? How would a 'social crisis' cause a wealthy and organised state to abandon effective armour production?

I would suggest that a lot of your ideas on this subject are based on a preexisting notion of 'decline and fall', which cannot be applied equally across the entire period of the 3rd-5th centuries, and in many cases is not supported by available evidence.