Is it really true that a seven-mile cross-country run is enforced upon all in this division, from generals to privates? ... It looks to me rather excessive. A colonel or a general ought not to exhaust himself in trying to compete with young boys running across country seven miles at a time. The duty of officers is no doubt to keep themselves fit, but still more to think of their men, and to take decisions affecting their safety and comfort. Who is the general of this division, and does he run the seven miles himself? If so, he may be more useful for football than for war. Could Napoleon have run seven miles across country at Austerlitz? Perhaps it was the other fellow he made run. In my experience, based on many years‘ observation, officers with high athletic qualifications are not usually successful in the higher ranks.
--Winston Churchill: Note for the Secretary of State for War, 4 February 1944
A man who takes a lot of exercise rarely exercises his mind adequately.
--B.H. Liddell Hart: Thoughts on War, xi, 1944
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Nations have passed away and left no traces,
And history gives the naked cause of it -
One single, simple reason in all cases,
They fell because their peoples were not fit.
--Rudyard Kipling: Land and Sea Tales for Scouts and Guides, 1923