The Use of Spies

Sunzi said: Generally, when mobilizing an army of a hundred thousand to campaign a thousand li away, the expenditures of the common people and the outlays of the state amount to a thousand pieces of gold daily. Both within and beyond the borders, there is commotion and unrest; those transporting supplies toil wearily on the roads, and as many as seven hundred thousand households are unable to engage in their normal farming.

The two sides are locked in stalemate for several years, all for the sake of seizing victory in a single day. If one begrudges ranks, salaries, and a hundred pieces of gold and refuses to use them to ascertain the enemy’s situation, that is the height of inhumanity. Such a person is unfit to be the commander of an army, unworthy to be the sovereign’s assistant, and cannot become the master of victory. Therefore, the wise sovereign and the competent general, when they act and conquer the enemy, achieving successes surpassing all others, do so because they can foresee the situation. To foresee the situation, one cannot seek it from ghosts and spirits, cannot infer it by analogy with similar events, and cannot verify it through the movements of the sun, moon, and stars; it must be obtained from people, specifically from those who know the enemy’s situation.

Thus, there are five types of spies to be employed: local spies, internal spies, converted spies, doomed spies, and surviving spies. When all five types are used simultaneously, the enemy cannot fathom the pattern, and this is called the “divine web,” the sovereign’s most precious asset. The local spy employs ordinary people from the enemy’s state. The internal spy employs officials from the enemy’s state. The converted spy employs the enemy’s own spies to serve as our spies. The doomed spy deliberately disseminates false information, letting our spy know it and then passing it to the enemy’s spy (so that the enemy is deceived, and our spy is often put to death). The surviving spy is one who can return alive to report the enemy’s situation.

Therefore, in the affairs of the three armies, no one is more intimate than the spy, no reward is more generous than that given to the spy, and no matter is more confidential than that concerning the spy. Only the sage and wise can employ spies; only the benevolent and righteous can drive spies; only those with subtle and ingenious minds can obtain true intelligence from spies.

Subtle indeed! Subtle indeed! There is no place where spies cannot be used. If the spy’s work has not yet begun but someone has already heard of it, then both the spy and the person who heard the news must be put to death.

Wherever the army is to attack an enemy force, assault a city, or kill an enemy person, one must first learn the names of the defending general, his close attendants, the officers in charge of communications and orders (yezhe), the gatekeepers, and the staff and retainers. Our spies must be ordered to investigate these thoroughly. One must seek out the enemy spies who have come to conduct espionage against us, then bribe and make use of them, guide them and then release them to return, so that converted spies can be employed. Through understanding gained from converted spies, local spies and internal spies can be employed. Through understanding gained from converted spies, doomed spies can disseminate false information and have it reported to the enemy. Through understanding gained from converted spies, surviving spies can return and report at the appointed time. The sovereign must understand the use of all five types of spies, and the key lies in the converted spy; therefore, the treatment of converted spies must be exceptionally generous.

In ancient times, the rise of the Shang dynasty occurred because Yi Yin had previously served as a spy in the Xia dynasty; the rise of the Zhou dynasty occurred because Jiang Ziya had previously served as a spy in the Shang dynasty. Thus, only the wise sovereign and the competent general, who can employ people of surpassing intelligence as spies, will surely achieve great success. This is the crucial point in military operations, and the entire army depends on the intelligence provided by spies to determine its actions.