The Abandonment of the Gladius for the Spatha - Why?

[Matthew]

Oh well, back to agreement, then. I have no problem with the crouched fighting stance, just the resting of one's shield on the ground whilst doing it. It's been a while since I read Connolly, my mistake. There's an article over at My Armoury that makes this claim about 'shield resting.' Judging by the bibliography and what I remembered of the book I mistakenly concluded that they were citing him:

http://www.myarmoury.com/feature_shield.html

I reached the same conclusion about the 'resting on one knee' in Vegetius. Interestingly, a similar passage turns up in Ambroises's 'Estoire De La Guerre Sainte':

'They went down on their knees , placing their round shields and long shields before them, lances* in their hands. The king, who was skilled in arms, had hidden behind the shields of two men, a crossbowman and another man to prepare his crossbow for him and hand it to him when he was ready. In this way the army was thoroughly protected.' [p. 183 of the translaton by Marianne Ailes].

*Apparently this is 'Glaive' and can be translated Spear / Lance or Sword...

Helmet development is an interesting potential indicator; I'm afraid my knowledge of the subject is too weak to comment, though.