If, however, you are indulgent, but unable to make your authority felt; kind-hearted, but unable to enforce your commands; and incapable, moreover, of quelling disorder: then your soldiers must be likened to spoilt children; they are useless for any practical purpose.
The general who advances without coveting fame and retreats without fearing disgrace, whose only thought is to protect his country and do good service for his sovereign, is the jewel of the kingdom.
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.
Spies cannot be usefully employed without a certain intuitive sagacity; They cannot be properly managed without benevolence and straightforwardness; Without subtle ingenuity of mind, one cannot make certain of the truth of their reports; Be subtle! be subtle! and use your spies for every kind of warfare; If a secret piece of news is divulged by a spy before the time is ripe, he must be put to death together with the man to whom the secret was told.
So in war, the way is to avoid what is strong and to strike at what is weak. Water shapes its course according to the nature of the ground over which it flows; the soldier works out his victory in relation to the foe whom he is facing.
When envoys are sent with compliments in their mouths, it is a sign that the enemy wishes for a truce. If the enemy's troops march up angrily and remain facing ours for a long time without either joining battle or removing demands, the situation is one that requires great vigilance and circumspection. To begin by bluster, but afterward to take fright at the enemy's numbers, shows a supreme lack of intelligence.
Should the enemy strengthen his van, he will weaken his rear; should he strengthen his rear, he will weaken his van; should he strengthen his left, he will weaken his right; should he strengthen his right, he will weaken his left. If he sends reinforcements everywhere, he will everywhere be weak.