On War (Original German title: Vom Kriege) was a book by Prussian General Carl von Clausewitz, who lived in the Napoleonic Era of the Final Age of Western Imperialism. Clausewitz wrote that war, politics, and diplomacy are all instruments of state policy. Written between 1816 and 1830 CE and published posthumously by his wife in 1832 CE, it was actually an unfinished work; Clausewitz had set about revising his accumulated manuscripts in 1827 CE, but did not live to finish the task. His wife eventually compiled all the work and the final two chapters her husband never finished.