[Wang Hsi thinks that this means not using the same stratagem twice.]
he keeps the enemy without definite knowledge.
[Chang Yu, in a quotation from another work, says: "The axiom, that war
is based on deception, does not apply only to deception of the enemy.
You must deceive even your own soldiers. Make them follow you, but
without letting them know why."]
By shifting his camp and taking circuitous routes, he prevents the
enemy from anticipating his purpose.