Chapter 13 — Use of Spies

Sunzi said: In general, when an army of one hundred thousand is raised and sent on a campaign a thousand miles away, the expenses of the common people and the outlays of the public treasury will amount to a thousand pieces of gold each day. There will be turmoil at home and abroad; men will collapse from exhaustion on the roads; and seven hundred thousand households will be unable to pursue their work. Armies may confront each other for several years to contend for victory on a single day. Yet if one begrudges ranks, emoluments, and a hundred pieces of gold and therefore remains ignorant of the enemy’s condition, this is the height of inhumanity. Such a man is no general of the people, no assistant to his ruler, and no master of victory. Thus, what enables enlightened rulers and worthy commanders to move and conquer others, achieving success beyond the multitude, is foreknowledge. Foreknowledge cannot be obtained from ghosts and spirits, cannot be inferred by analogy from events, and cannot be verified by calculations. It must be obtained from men who know the enemy’s condition.

Therefore, there are five kinds of spies: local spies, inside spies, turned spies, doomed spies, and surviving spies. When all five kinds are active together and no one knows their methods, this is called the “divine web,” and it is the treasure of the ruler. Local spies are recruited from among the enemy’s local people. Inside spies are recruited from among the enemy’s officials. Turned spies are recruited from among the enemy’s spies. Doomed spies carry deceptive information abroad: we let our own spies know it and have them transmit it to the enemy’s spies. Surviving spies return to report.

Thus, among all affairs of the three armies, none is more intimate than relations with spies; no rewards are richer than those given to spies; no affairs are more secret than matters of espionage. Without sagely wisdom, one cannot employ spies; without benevolence and righteousness, one cannot command spies; without subtlety and discernment, one cannot obtain the truth from spies. Subtle indeed! Subtle indeed! There is nowhere that spies cannot be employed. If a matter of espionage is heard before it has been carried out, both the spy and the person to whom he disclosed it must die.

Whenever there is an army you wish to strike, a city you wish to attack, or a person you wish to kill, you must first know the names of the defending commander, his attendants, his ushers, his gatekeepers, and his chamberlains. Order your spies to investigate and learn them all. Enemy spies who have come to spy upon us must be sought out. Lure them with profit, guide them, and lodge them; thus turned spies can be obtained and employed. Through the knowledge gained from them, local spies and inside spies can be found and employed. Through the knowledge gained from them, doomed spies can carry deceptive information to the enemy. Through the knowledge gained from them, surviving spies can return as scheduled. The ruler must know the affairs of all five kinds of spies, and this knowledge must come from turned spies. Therefore, turned spies must be treated with the utmost generosity.

Formerly, when Yin arose, Yi Zhi was in Xia; when Zhou arose, Lü Ya was in Yin. Therefore, enlightened rulers and worthy commanders who can employ men of supreme wisdom as spies will surely accomplish great achievements. This is the essential matter in warfare, upon which the three armies rely in order to move.

Sunzi said: In general, when an army of a hundred thousand is raised and sent on a campaign a thousand miles away, the people’s expenses and the state’s expenditures amount to a thousand pieces of gold a day. There is turmoil at home and abroad, people are exhausted on the roads, and seven hundred thousand households are unable to pursue their work. Armies may confront each other for several years to contend for victory on a single day. If, out of reluctance to spend rank, salary, and a hundred pieces of gold, one fails to learn the enemy’s situation, this is the height of inhumanity. Such a person is no commander of men, no assistant to a ruler, and no master of victory. What enables enlightened rulers and worthy commanders to move and defeat others, achieving successes beyond the multitude, is foreknowledge. Foreknowledge cannot be obtained from ghosts and spirits, cannot be inferred from analogous events, and cannot be verified by calculations. It must be obtained from people who know the enemy’s situation.

Therefore, there are five kinds of spies: local spies, inside spies, converted spies, doomed spies, and surviving spies. When all five kinds operate together and no one knows their methods, this is called the “divine web,” and it is a ruler’s treasure. Local spies are recruited from the enemy’s local people. Inside spies are recruited from the enemy’s officials. Converted spies are recruited from the enemy’s spies. Doomed spies are used when we spread deceptive information outside, let our own spies know it, and have them transmit it to the enemy’s spies. Surviving spies are those who return with reports.

Therefore, of all relationships in the army, none should be closer than that with spies; no rewards should be more generous than those given to spies; and no affairs should be more secret than espionage. Without sagacious wisdom, one cannot employ spies. Without benevolence and righteousness, one cannot use spies effectively. Without subtlety and ingenuity, one cannot obtain the truth from spies. Subtle, so subtle! There is nowhere spies are not employed. If an espionage operation has not yet been carried out but is heard of in advance, both the spy and the person he told must be put to death.

Whenever there is an army we wish to strike, a city we wish to attack, or a person we wish to kill, we must first learn the names of the defending commander, his attendants, those who announce visitors, the gatekeepers, and the members of his staff. Order our spies to seek out and learn all of them. We must seek out enemy spies who have come to spy on us, then bribe them, guide them, and lodge them well. In this way, converted spies can be obtained and employed. Through the information gained from them, local spies and inside spies can be found and employed. Through the information gained from them, deceptive operations can be devised so that doomed spies can transmit false information to the enemy. Through the information gained from them, surviving spies can be sent and made to return at the appointed time. The ruler must know the work of all five kinds of spies, and this knowledge must depend on converted spies. Therefore, converted spies must be treated with the greatest generosity.

In ancient times, when the Yin rose to power, Yi Zhi was in Xia. When the Zhou rose to power, Lü Ya was in Yin. Therefore, an enlightened ruler or worthy commander who can use people of the highest wisdom as spies will certainly accomplish great achievements. This is the essential element of warfare, on which the entire army relies in order to move.