Very interesting good post.
Read up if yah like on Rommel's Africa corps and the correlation of their field rations and ability to fight. Surprisingly a key ingredient in Rommel's failures in Africa was not the ability of his troops to fight but their problems with rations.
Their foods were greasy, out of date and it was making his men sick. The allies were not serving steak and lobster but enough nourishing foods to keep the men on top of things.
How does that saying go? "An Army travels on its stomach."