Karl von Clausewitz
Carl Phillip Gottlieb von Clausewitz (June 1, 1780 - November 16, 1831) was a Prussian military thinker.
Despite never completing (On War), his ideas have been widely influencial in military theory.
He is perhaps most quoted on the idea that war -- violent military action -- is only the 'strong arm' of diplomacy, utilized when more peaceful means of persuasion are not sufficient.
He married Countess Marie von Brühl.
See also: Famous military writers