XIII. THE USE OF SPIES

by Sun Tzu

　　1. Sun Tzu said: Raising a host of a hundred thousandmen and marching them great distances entails heavy losson the people and a drain on the resources of the State.The daily expenditure will amount to a thousand ouncesof 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 impededin 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'scondition simply because one grudges the outlay of a hundredounces of silver in honors and emoluments, is the heightof inhumanity. 3. One who acts thus is no leader of men, no presenthelp to his sovereign, no master of victory. 4. Thus, what enables the wise sovereign and the goodgeneral to strike and conquer, and achieve things beyondthe 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 onlybe 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 "divinemanipulation of the threads." It is the sovereign'smost precious faculty. 9. Having local spies means employing the servicesof the inhabitants of a district. 10. Having inward spies, making use of officialsof the enemy. 11. Having converted spies, getting hold of the enemy'sspies and using them for our own purposes. 12. Having doomed spies, doing certain things openlyfor purposes of deception, and allowing our spies to knowof them and report them to the enemy. 13. Surviving spies, finally, are those who bringback news from the enemy's camp. 14. Hence it is that which none in the whole army aremore intimate relations to be maintained than with spies.None should be more liberally rewarded. In no otherbusiness should greater secrecy be preserved. 15. Spies cannot be usefully employed without a certainintuitive sagacity. 16. They cannot be properly managed without benevolenceand straightforwardness. 17. Without subtle ingenuity of mind, one cannot makecertain of the truth of their reports. 18. Be subtle! be subtle! and use your spies for everykind of business. 19. If a secret piece of news is divulged by a spybefore the time is ripe, he must be put to death togetherwith the man to whom the secret was told. 20. Whether the object be to crush an army, to storma city, or to assassinate an individual, it is alwaysnecessary to begin by finding out the names of the attendants,the aides-de-camp, and door-keepers and sentries of the generalin command. Our spies must be commissioned to ascertain these. 21. The enemy's spies who have come to spy on usmust be sought out, tempted with bribes, led away andcomfortably housed. Thus they will become convertedspies and available for our service. 22. It is through the information brought by theconverted spy that we are able to acquire and employlocal and inward spies. 23. It is owing to his information, again, that we cancause the doomed spy to carry false tidings to the enemy. 24. Lastly, it is by his information that the survivingspy can be used on appointed occasions. 25. The end and aim of spying in all its five varietiesis knowledge of the enemy; and this knowledge can onlybe derived, in the first instance, from the converted spy.Hence it is essential that the converted spy be treatedwith the utmost liberality. 26. Of old, the rise of the Yin dynasty was due to IChih who had served under the Hsia. Likewise, the riseof the Chou dynasty was due to Lu Ya who had servedunder the Yin. 27. Hence it is only the enlightened ruler and thewise general who will use the highest intelligence ofthe army for purposes of spying and thereby they achievegreat results. Spies are a most important element in water,because on them depends an army's ability to move.