" The basic reason for German failure at the Marne, “the reason that transcends all others,” said Kluck afterward, was “the extraordinary and peculiar aptitude of the French soldier to recover quickly. That men will let themselves be killed where they stand, that is a well-known thing and counted on in every plan of battle. But that men who have retreated for ten days, sleeping on the ground and half dead with fatigue, should be able to take up their rifles and attack when the bugle sounds, is a thing upon which we never counted. It was a possibility not studied in our war academy. "

― Barbara W. Tuchman , The Guns of August