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.

The natural formation of the country is the soldier's best ally

You can ensure the success of your attacks if you only attack places that are undefended. You can ensure the safety of your defense if you only hold positions that cannot be attacked. Therefore, that general is skillful in attack whose opponent does not know what to defend; and he is skillful in defense whose opponent does not know what to attack.

One need not destroy one's enemy. One need only destroy his willingness to engage.

Invincibility depends on one's self; the enemy's vulnerability on him.

The King is only fond of words, and cannot translate them into deeds.

Those who would wage war, should first eliminate all domestic enemies before proceeding to attack the external foe.