Carl von Clausewitz (1780–1831) was an early 19th-century German military theorist; was in the service of the Russian Emperor throughout the Patriotic War of 1812 and fought, in essence, against his country, Prussia, which was an ally of Napoleon. Clausewitz's theory has always played a big role in Russia. Clausewitz's thoughts on war seemed so important to Leo Tolstoy that he included this Prussian general in his epic War and Peace. Leo Tolstoy was very familiar with both Clausewitz's book On War and his multi-volume work The War of 1812 in Russia,” and at least on one point, as a historiosophist, he decisively disagrees with the German military theorist and practitioner: for Tolstoy, war is a senseless and fatal phenomenon, but the basis of Clausewitz’s entire teaching about war is his famous formula: “War is a continuation politics in other ways.” Clausewitz largely based his theory on the experience of Russian victories in 1812. In his book about the war of 1812, he gives a very high assessment of Russian commanders. In their actions, Carl von Clausewitz saw confirmation of his military doctrine.