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

16. The spot where we intend to fight must not be made known; for then

the enemy will have to prepare against a possible attack at several different points; [Sheridan once explained the reason of General Grant’s victories by saying that "while his opponents were kept fully employed wondering what he was going to do, _he_ was thinking most of what he was going to do himself."] and his forces being thus distributed in many directions, the numbers we shall have to face at any given point will be proportionately few.