The enemy's spies who have come to spy on us must be sought out, tempted with bribes, led away and comfortably housed. Thus they will become double agents and available for our service. It is through the information brought by the double agent that we are able to acquire and employ local and inward spies. It is owing to his information, again, that we can cause the doomed spy to carry false tidings to the enemy.

What is of the greatest importance in war is extraordinary speed: One cannot afford to neglect opportunity.

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 the thunderclap comes, there is no time to cover the ears.

Where the army is, prices are high; when prices rise the wealth of the people is exhausted.

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

And therefore those skilled in war bring the enemy to the field of battle and are not brought there by him.