Section 13

The Use of Spies explained simply

The Art of War by Sun Tzu

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Sun Tzŭ said: Raising a host of a hundred thousand men and marching them great distances entails heavy loss on the people and a drain on the resources of the State.
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Chapter XIII. THE USE OF SPIES 1. Sun Tzŭ said: Raising a host of a hundred thousand men and marching them great distances entails heavy loss on the people and a drain on the resources of the State. The daily expenditure will amount to a thousand ounces of silver. There will be commotion at home and abroad, and men will drop down exhausted on the highways. As many as seven hundred thousand families will be impeded in their labor. 2. Hostile armies may face each other for years, striving for the victory which is decided in a single day. This being so, to remain in ignorance of the enemy’s condition simply because one grudges the outlay of a hundred ounces of silver in honours and emoluments, is the height of inhumanity. 3. One who acts thus is no leader of men, no present help to his sovereign, no master of victory. 4. 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_. 5. Now this foreknowledge cannot be elicited from spirits; it cannot be obtained inductively from experience, nor by any deductive calculation. 6. Knowledge of the enemy’s dispositions can only be obtained from other men. 7. Hence the use of spies, of whom there are five classes: (1) Local spies; (2) inward spies; (3) converted spies; (4) doomed spies; (5) surviving spies. 8. When these five kinds of spy are all at work, none can discover the secret system. This is called "divine manipulation of the threads." It is the sovereign’s most precious faculty. 9. Having _local spies_ means employing the services of the inhabitants of a district. 10. Having _inward spies_, making use of officials of the enemy. 11. Having _converted spies_, getting hold of the enemy’s spies and using them for our own purposes. 12. Having _doomed spies_, doing certain things openly for purposes of deception, and allowing our own spies to know of them and report them to the enemy. 13. _Surviving spies_, finally, are those who bring back news from the enemy’s camp. sent Ta-hsi Wu to spy upon the enemy. He was accompanied by two other men. All three were on horseback and wore the enemy’s uniform. When it was dark, they dismounted a few hundred feet away from the enemy’s camp and stealthily crept up to listen, until they succeeded in catching the passwords used in the army. Then they got on their horses again and boldly passed through the camp under the guise of night-watchmen; and more than once, happening to come across a soldier who was committing some breach of discipline, they actually stopped to give the culprit a sound cudgeling! Thus they managed to return with the fullest possible information about the enemy’s dispositions, and received warm commendation from the Emperor, who in consequence of their report was able to inflict a severe defeat on his adversary."] 14. Hence it is that with none in the whole army are more intimate relations to be maintained than with spies. None should be more liberally rewarded. In no other business should greater secrecy be preserved. 15. Spies cannot be usefully employed without a certain intuitive sagacity. 16. They cannot be properly managed without benevolence and straightforwardness. 17. Without subtle ingenuity of mind, one cannot make certain of the truth of their reports. 18. Be subtle! be subtle! and use your spies for every kind of business. 19. 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. 20. Whether the object be to crush an army, to storm a city, or to assassinate an individual, it is always necessary to begin by finding out the names of the attendants, the aides-de- camp, the door-keepers and sentries of the general in command. Our spies must be commissioned to ascertain these. 21. 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 converted spies and available for our service. 22. It is through the information brought by the converted spy that we are able to acquire and employ local and inward spies. 23. It is owing to his information, again, that we can cause the doomed spy to carry false tidings to the enemy. 24. Lastly, it is by his information that the surviving spy can be used on appointed occasions. 25. The end and aim of spying in all its five varieties is knowledge of the enemy; and this knowledge can only be derived, in the first instance, from the converted spy. Hence it is essential that the converted spy be treated with the utmost liberality. 26. Of old, the rise of the Yin dynasty who had served under the Hsia. Likewise, the rise of the Chou dynasty was due to Lü Ya who had served under the Yin. 27. Hence it is only the enlightened ruler and the wise general who will use the highest intelligence of the army for purposes of spying and thereby they achieve great results. Spies are a most important element in war, because on them depends an army’s ability to move.

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Simple English explanation

Good information is a strategic advantage. Learn from reliable sources before committing people and resources. Acting without knowledge turns courage into gambling.

1-minute summary

The Use of Spies explains that good information is a strategic advantage. In practice, learn from reliable sources before committing people and resources. It also warns that acting without knowledge turns courage into gambling. The useful lesson is to make the wise move early, while the situation is still small enough to guide.

Key takeaways

  • Good information is a strategic advantage.
  • Learn from reliable sources before committing people and resources.
  • Acting without knowledge turns courage into gambling.
  • Use the idea in one concrete decision today.

Modern example

A founder should interview real customers before building a feature based only on internal opinions.

For kids

Ask and learn before you guess.