“Warfare is mental, not physical.”
General Bruce Cooper Clarke (-1988)
US Army General who served in WW1, WW2 (awarded three Silver Stars) and the Korean War. Graduated from West Point as an engineer in 1925 and transferred to Armour in 1942, before specialising in the organisation and training of soldiers in 1945 (Hess, 1970).
The Harry S Truman Library and Museum has a good interview with, and associated documents by, General Clarke (see Reference).
Hess, J.N. (1970) Oral History Interview with Bruce C. Clarke. Available from World Wide Web: https://www.trumanlibrary.org/oralhist/clarkeb.htm. [Accessed: 03 January, 2016].