Hence the saying: If you know the enemy and you know yourself, your victory will not stand in doubt; if you now Heaven and you know Earth, you may make your victory complete.

Unless you enter the tiger's lair, you cannot get hold of the tiger's cub's.

All war is deception.

If the enemy opens the door, you must race in.

When the enemy's envoy's speak in humble terms, but continues his preparations, he will advance. When their language is deceptive but the enemy pretentiously advances, he will retreat. When the envoys speak in apologetic terms, he wishes a respite. When without a previous understanding the enemy asks for a truce, he is plotting. When the enemy sees an advantage but does not advance to seize it, he is fatigued.

For the wise man delights in establishing his merit, the brave man likes to show his courage in action, the covetous man is quick at seizing advantages, and the stupid man has no fear of death.

Probe him and learn where his strength is abundant and where deficient.