Bodily Exertion
Clausewitz says that bodily exertion and fatigue in war "put fetters on the action of the mind, and wear out in secret the powers of the soul." "Like danger, they belong to the fundamental causes of friction."[36]
To one who, like Clausewitz, had seen the retreat from Moscow, the awful passage of the Beresina, and the battle of the nations round Leipzig, bodily exertion could not be overlooked. Had he not seen bodily exertion and hardship break up the Grand Army into a small horde of stragglers, and destroy the army of Kutusoff in almost an equal measure, in 1812, as well as practically ruin the spirit, and largely break up the great army of Napoleon in 1813?
As for the effects of bodily exertion on the mind, purpose, and resolution of the general, compare Benningsen at Eylau after thirty-six hours in the saddle, or Napoleon at Dresden, by which he lost all the results of his victory.