Chapter 13, Verses 2 and 3 - Sun Tzu

Hostile armies may face each other for years, striving for the victory which is decided in a single day. This being so, to remain in ignorance of the enemy's condition simply because one grudges the outlay of a hundred ounces of silver in honors and emoluments, is the height of inhumanity. One who acts thus is no leader of men, no present help to his sovereign, no master of victory.
~ from The Art of War, Giles translation ~

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