Chapter 3, Verse 17 - Sun Tzu

Thus we may know that there are five essentials for victory: (1) He will win who knows when to fight and when not to fight. (2) He will win who knows how to handle both superior and inferior forces. (3) He will win whose army is animated by the same spirit throughout all its ranks. (4) He will win who, prepared himself, waits to take the enemy unprepared. (5) He will win who has military capacity and is not interfered with by the sovereign.
~ from The Art of War, Giles translation ~

Go here to read the introductory post to the verses of The Art of War.