Carl von Clausewitz The Prussian Major General Carl von Clausewitz (1780-1831) was a military reformer and strategist, and one of the leading military thinkers of the nineteenth century. In many respects, Clausewitz's theory of war, put forth in his major work On War (1832), represented a paradigmatic shift in military thinking, because it considered the fundamental relationship between war and politics. Lithograph by Franz Michaelis after a missing painting by Karl Wilhelm Wach.