If you know yourself but not the enemy, for every victory gained you will also suffer a defeat.

It is ten thousand times cheaper to pay the best spies lavishly than even a tiny army poorly.

Now this foreknowledge cannot be elicited from spirits; it cannot be obtained inductively from experience, nor by any deductive calculation.

Concentrate your energy and hoard your strength.

Unless you know the mountains and the forests, the defiles and impasses, the lay of the marshes and swamps, you cannot maneuver with an armed force. Unless you use local guides, you cannot get the advantages of the land.

There is no instance of a nation benefiting from prolonged warfare.

Against those skilled in attack, an enemy does not know where to defend; against the experts in defense, the enemy does not know where to attack.