On War (German Vom Kriege) is a book on military strategy and tactics by Prussian general Carl von Clausewitz, written mostly after the Napoleonic wars, between 1816 and 1818, and published posthumously by his wife in 1832. It is one of the most important treatises on strategy ever written, and is prescribed at various military academies to this day.
On War is actually an unfinished work; Clausewitz had set about revising his accumulated manuscripts in 1827, but did not live to finish the task.
The West's modern perception of war is based on the Clausewitzian principles taught in On War. Its military doctrine, organization, and norms are all based on Clausewitzian premises, even to this day.
On War has been seen as the place where the concept of total war was made explicit and has been blamed1 for the level of destruction involved in the First and Second World War, whereas it seems rather that Clausewitz had merely foreseen the inevitable development starting with the huge, patriotically motivated armies of the Napoleonic wars and resulting (though not ending) in the atomic bombs on Hiroshima and Nagasaki, with all forces and capabilities of a state devoted to destroying forces and capabilities of the enemy state (thus "total war").
The book contains a wealth of historical examples used to illustrate the various concepts. Frederick II of Prussia (the Great) figures prominently for having made very efficient use of the limited forces at his disposal. Napoleon also is a central figure.
On War is a work rooted solely in the world of the state. Martin Van Creveld states that Clausewitz takes the state "almost for granted" as he rarely looks at anything previous to Westphalia. He does not address any form of intra/supra-state conflict, such as rebellion, because he could theoretically not account for warfare before the existence of the state. Previous kinds of conflict were demoted to criminal activities without legitimacy and not worthy of a declaration of war. Clausewitz explains that war requires the state to act in conjunction with the people and the army, the state becoming a massive engine built to exude military force against an identical opponent. This statement is easily verified by looking at the conventional armies in existence throughout the 20th century.