Keep their friends close and their enemies closer.

When you know both yourself as well as your competition, you are never in danger. To know yourself and not others, gives you half a chance of winning. Knowing neither yourself or your competition puts you in a position to lose.

By altering his arrangements and changing his plans, the skillful general keeps the enemy without definite knowledge. By shifting his camp and taking circuitous routes, he prevents the enemy from anticipating his purpose. At the critical moment, the leader of an army acts like one who has climbed up a height and then kicks away the ladder behind him.

Perfection in war lies in so sapping your opponents will that he surrenders without fighting.

Thus those skilled in war subdue the enemy's army without battle .... They conquer by strategy.

One defends when his strength is inadequate, he attacks when it is abundant.

Correct your mistake as soon as you have found it.