If your opponent is of choleric temper, seek to
irritate him. Pretend to be weak, that he may grow
arrogant. If he is taking his ease, give him no
rest. If his forces are united, separate them. Attack
him where he is unprepared, appear where you are not
expected. These military devices, leading to victory,
must not be divulged beforehand.

        -- Sun Tzu
           The Art of War