The Use of Spies

R aise a hundred thousand men and march them a thousand li, and the cost falls on everyone. The people are bled. The treasury is drained. A thousand pieces of gold go out every day. Inside the country and along the roads there is turmoil; seven hundred thousand households are kept from their own work. When you raise an army of a hundred thousand and march it out a thousand li, the expense to the common people and the outlay of the state come to a thousand pieces of gold a day. There is upheaval at home and abroad; men are worn out on the roads, and seven hundred thousand households are unable to attend to their work.

Two armies can sit facing each other for years, all of it spent to decide a single day's fighting. And after that ruinous outlay, a commander grudges a few honors and a little gold — and so never learns the enemy's true state. That is the height of inhumanity. Armies may hold against each other for years, all in order to contend for victory in a single day. And then to grudge ranks, pay, and a hundred pieces of gold, and so remain ignorant of the enemy's condition — that is the extreme of inhumanity.

A man like that is no leader of armies, no help to his lord, no master of victory. What lets a wise ruler and a good general strike and win, and outdo other men, is one thing: they know first. Such a man is no general of his troops, no aid to his ruler, no master of victory. What allows an enlightened ruler and a wise general to move and overcome others, and to achieve beyond the common run, is foreknowledge.

“What lets a wise ruler and a good general strike and win, and outdo other men, is foreknowledge.”

This foreknowledge cannot be begged from gods or ghosts. It cannot be read off past events by analogy. It cannot be reckoned out by measuring the heavens. It has to be got from men — from people who know the enemy's real condition. This foreknowledge cannot be obtained from spirits, nor inferred from appearances, nor checked against calculations. It must be got from men — from those who know the enemy's true state.

So there are five kinds of spy: the local spy, the inside spy, the turned spy, the doomed spy, and the living spy. Set all five working at once and no one can trace the pattern of it. This is the hidden web — a ruler's treasure. Hence there are five kinds of spy: the local spy, the inward spy, the converted spy, the doomed spy, and the living spy. When all five are at work together and none can discover their method, this is called the divine web — the ruler's treasure.

Local spies you draw from the enemy's own countryfolk. Inside spies you draw from his officials. Turned spies you draw from his agents — his spies, taken and used against him. Local spies are recruited from the people of the enemy's district. Inward spies are recruited from his officials. Converted spies are the enemy's own spies, taken and used in return.

Doomed spies you send to die. You set up a false story, let your own agent believe it, and let him carry it across to the enemy. Living spies are the ones who come back to report. Doomed spies do something deceptive abroad: we let our own agent know of it, and he passes it to the enemy. Living spies are those who return to report.

So in the whole army no one is closer to you than your spies, none rewarded more richly, no business kept more secret. Without deep wisdom you cannot use them. Without humanity and fairness you cannot direct them. Without subtlety you cannot get the truth out of them. Of all in the army, none is on closer terms than the spy; none is more liberally rewarded; in no other business is greater secrecy kept. Without sagacity you cannot use spies; without humanity and justice you cannot direct them; without subtle ingenuity you cannot get the truth from them.

Subtle, always subtle. There is no place where you do not use spies. But if a spy's report leaks out before its time, the spy and the man he told it to must both die. Subtle indeed, subtle — there is nowhere spies cannot be used. If a spy's business is disclosed before the time, the spy and the one he informed must both be put to death.

When you mean to strike an army, storm a town, or kill a particular man, first find out the names: the defending general, his aides, his gatekeepers, his attendants. Set your spies to dig out every one. Whenever you wish to attack an army, besiege a city, or assassinate a man, you must first know the names of the defending general, his attendants, the men who carry word, the gatekeepers, and the household staff. Direct your spies to seek all of this out.

Hunt down the enemy's agents who have come to spy on you. Win them with gain, guide them, house them — and so the turned spy is made and put to work. Through what he tells you, you can raise local spies and inside spies. Through it you can feed the doomed spy his false tale to carry over. Through it the living spy can keep to his schedule. You must seek out the enemy's spies who have come to spy on us, tempt them with advantage, guide them, and lodge them — and so the converted spy can be obtained and used. Through his knowledge you can recruit local and inward spies. Through it the doomed spy can be sent with false reports to the enemy. Through it the living spy can be used as planned.

All five kinds of spy depend on the turned spy, so the ruler must know him through and through. And that is exactly why the turned spy must be paid the most lavishly of all. The ruler must know all five sorts of spy work, and that knowledge always depends on the converted spy — which is why the converted spy must be treated with the utmost generosity.

When the Yin dynasty rose, it had Yi Zhi, who had served the fallen Xia. When the Zhou rose, it had Lü Ya, who had served the Yin. So only the wise ruler and the able general, who can make their best minds into spies, are sure of great results. This is the heart of warfare — what the whole army leans on to move at all. When the Yin dynasty rose, Yi Zhi was in Xia; when the Zhou rose, Lü Ya was in Yin. So only an enlightened ruler and a worthy general, able to use the highest intelligence for spying, are certain of great achievement. This is the essence of war — what the whole army depends on in every move.

用間 The original Chinese · honored as an artifact

孫子曰：凡興師十萬，出征千里，百姓之費，公家之奉，日費千金，內外騷動，怠于道路，不得操事者，七十萬家。

Opening lines, classical Chinese · The Art of War 孫子兵法