Except for a brief stint in 1812 when he served in the Russian army, Clausewitz spent his whole career, from the age of twelve until his death in 1831, in the Prussian army. He fought in all the major Prussian campaigns against France, and his most fateful experience - the 1806 Battle of Jena-Auerstedt, in which Napoleon destroyed the Prussian army - inspired him to write