The Art of War by active 6th century B.C. Sunzi

31. Hence the saying: If you know the enemy and know yourself, your

victory will not stand in doubt; if you know Heaven and know Earth, you may make your victory complete. [Li Ch’uan sums up as follows: "Given a knowledge of three things—the affairs of men, the seasons of heaven and the natural advantages of earth—, victory will invariably crown your battles."] [1] See "Pensees de Napoleon 1er," no. 47. [2] "The Science of War," chap. 2. [3] "Aids to Scouting," p. xii.