In warfare, first lay plans which will ensure victory, and then lead your army to battle; if you will not begin with stratagem but rely on brute strength alone, victory will no longer be assured.
It is essential to seek out enemy agents who have come to conduct espionage against you and to bribe them to serve you. Give them instructions and care for them. Thus doubled agents are recruited and used.
Humble words and increased preparations are signs that the enemy is about to advance. Violent language and driving forward as if to the attack are signs that he will retreat.
Now the reason the enlightened prince and the wise general conquer the enemy whenever they move and their achievements surpass those of ordinary men is foreknowledge.
Generally, management of many is the same as management of few. It is a matter of organization. And to control many is the same as to control few. This is a matter of formations and signals.
In all history, there is no instance of a country having benefited from prolonged warfare. Only one who knows the disastrous effects of a long war can realize the supreme importance of rapidity in bringing it to a close.
The sovereign must have full knowledge of the activities of the five sorts of agents. This knowledge must come from the double agents, and therefore it is mandatory that they be treated with the utmost liberality.
To plan secretly, to move surreptitiously, to foil the enemy's intentions and balk his schemes, so that at last the day may be won without shedding a drop of blood.