<human>:  Where does the phrase ‘the art of war’ come from?
<bot>: The phrase “the art of war” comes from a line in The Art of War. In the book, Sun Tzu wrote: "If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle."