The Art of War · Chapter

XIII: The Use of Spies explained

Sun Tzǔ emphasizes the critical importance of foreknowledge in warfare, arguing that the cost of maintaining spies is negligible compared to the waste of prolonged conflict.

What happens

Sun Tzǔ emphasizes the critical importance of foreknowledge in warfare, arguing that the cost of maintaining spies is negligible compared to the waste of prolonged conflict. He outlines five types of spies—local, inward, converted, doomed, and surviving—and explains how they must be employed with secrecy, liberality, and subtlety. The chapter concludes with historical examples of dynastic rises enabled by spies and declares that spies are essential for an army's ability to act.

Themes in this chapter

Deception and Stratagem
The entire chapter focuses on espionage as a form of deception, including the use of doomed spies to feed false information to the enemy.
Economy of Force and Minimal Bloodshed
Sun Tzǔ argues that spending on spies is far less costly than the human and material waste of prolonged war, aiming to achieve victory with minimal loss.
Psychology and Morale
The chapter stresses the need for subtlety, benevolence, and secrecy in handling spies, highlighting the psychological dimensions of intelligence work.

Characters to notice

Sun Tzǔ
Author of the chapter, presenting the doctrine on espionage and foreknowledge.
I Chih
Mentioned as a spy who served under the Hsia and contributed to the rise of the Yin dynasty.
Lu Ya
Mentioned as a spy who served under the Yin and contributed to the rise of the Chou dynasty.

Key passages

“Thus, what enables the wise sovereign and the good general to strike and conquer, and achieve things beyond the reach of ordinary men, is foreknowledge.”
The ability of a wise ruler or skilled general to attack and win, accomplishing what others cannot, comes from knowing the enemy's situation in advance.
Sun Tzǔ establishes foreknowledge as the key to strategic success.
“Knowledge of the enemy’s dispositions can only be obtained from other men.”
Information about the enemy's plans and positions must come from human sources, not supernatural or abstract methods.
Emphasizes the necessity of espionage over divination or reasoning.
“Spies cannot be usefully employed without a certain intuitive sagacity.”
Effective use of spies requires a natural shrewdness and insight.
Highlights the need for intelligence and judgment in handling espionage.

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