Place your army in deadly peril, and it will survive; plunge it into desperate straits, and it will come off in safety.

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.

Winning isn't enough. The acme of all skill is to defeat your enemy before taking the field.

In all fighting, the direct method may be used for joining battle, but indirect methods will be needed in order to secure victory. Indirect tactics, efficiently applied, are inexhaustible as Heaven and Earth, unending as the flow of rivers and streams; like the sun and moon, they end but to begin anew; like the four seasons, they pass away to return once more.

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

The relative size of your force as against that of your adversary is by itself of no consequence. What controls is the relative size of your force at the point where you join in battle. You can strike with the few and be many if you strike your adversary in his gaps. Seek out places where the defense is not strict, the place not tightly guarded, the generals weak, the troops disorderly, the supplies are scarce and the forces are isolated.

Bring war material with you from home, but forage on the enemy... use the conquered foe to augment one's own strength.