Carl Phillip Gottleib von Clausewitz (1780-1831) was a Prussian soldier and intellectual. He came from a humble social background, though his family claimed nobility. He served as a practical field soldier (with extensive combat experience against the armies of the French Revolution and Napoleon), as a staff officer with political/military responsibilities at the very center of the Prussian state, and as a prominent military educator. Clausewitz first entered combat as a cadet at the age of 13, rose to the rank of Major-General at 38, married into the high nobility, moved in rarefied intellectual cirles in Berlin, and wrote a book which has become the most influential work of military philosophy in the Western world.
Sorry to have confused you. We were actually discussing Machiavelli, and his book The Art of War, not Clausewitz (I posted a list of his quotations earlier this week). I am well aware of the Baron's military experience - but good addition to the thread anyway.