12. In every army, the five developments connected with fire must be known, the movements of the stars calculated, and a watch kept for the proper days.
13. Hence those who use fire as an aid to the attack show intelligence; those who use water as an aid to the attack gain an accession of strength.
14. By means of water, an enemy may be intercepted, but not robbed of all his belongings.
15. Unhappy is the fate of one who tries to win his battles and succeed in his attacks without cultivating the spirit of enterprise; for the result is waste of time and general stagnation.
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16. Hence the saying: The enlightened ruler lays his plans well ahead; the good general cultivates his resources.
17. Move not unless you see an advantage; use not your troops unless there is something to be gained; fight not unless the position is critical.
18. No ruler should put troops into the field merely to gratify his own spleen; no general should fight a battle simply out of pique.
19. If it is to your advantage, make a forward move; if not, stay where you are.
20. Anger may in time change to gladness; vexation may be succeeded by content.
21. But a kingdom that has once been destroyed can never come again into being; nor can the dead ever be brought back to life.
22. Hence the enlightened ruler is heedful and the good general full of caution. This is the way to keep a country at peace and an army intact.
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Sun Tzu on the Art of War
XIII
The Use of Spies
1. Sun Tzu 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, striv-ing 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 honors 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.
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Sun Tzu on the Art of War
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 class-es:
(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 spies to know of them and report them to the enemy.
