from Wu Chi's Art of War

When fierce bandits come you must take precautions against them. It is best to stand on the defensive and not meet them. When at dusk they are about to depart laden and encumbered with loot they are certain to be apprehensive, for their withdrawal is by distant routes and they must travel fast. There are certain to be some who lag behind. Follow them and strike and you can rout them.

-taken from Appendix I of Sun Tzu's Art of War, Griffith translation