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

For them to perceive the advantage of defeating the enemy, they must also have their rewards.

Opportunities increase as they are taken.

Therefore I say: know the enemy and know yourself; in a hundred battles you will never be in peril. When you are ignorant of the enemy but know yourself, your chances of winning or losing are equal. If ignorant both of your enemy and of yourself, you are certain in every battle to be in peril.

When you shoot a bow and arrow, you aim at the clouds, not because you expect to hit them, but so that you may reach the distant target on the ground.

Invincibility is in oneself, and vulnerability is in the opponent. Invincibility is a matter of defense, vulnerability is a matter of attack. Therefore skillful warriors are able to be invincible, but they cannot cause opponents to be vulnerable. That is why it is said that victory is discerned and not manufactured.

Prohibit the taking of omens, and do away with superstitious doubts. Then, until death itself comes, no calamity need be feared.