Chapter 13 of Sun Tzu

孙Sūn子zǐ曰yuē：凡fán兴xīng师shī十shí万wàn，出chū征zhēng千qiān里lǐ，百bǎi姓xìng之zhī费fèi，公gōng家jiā之zhī奉fèng，日rì费fèi千qiān金jīn，内nèi外wài骚sāo动dòng，怠dài于yú道dào路lù，不bù得dé操cāo事shì者zhě，七qī十shí万wàn家jiā。相xiāng守shǒu数shù年nián，以yǐ争zhēng一yī日rì之zhī胜shèng，而ér爱ài爵jué禄lù百bǎi金jīn，不bù知zhī敌dí之zhī情qíng者zhě，不bù仁rén之zhī至zhì也yě，非fēi民mín之zhī将jiàng也yě，非fēi主zhǔ之zhī佐zuǒ也yě，非fēi胜shèng之zhī主zhǔ也yě。

Sun Tzu said: Raising an army of one hundred thousand men and sending troops a thousand li away involves expenses for the people and the state, with daily costs of one thousand pieces of gold. Inside and outside, everything is in turmoil; people are exhausted on the roads, and seven hundred thousand households cannot attend to their affairs. If, after years of preparation for a decisive battle of a single day, one hesitates to spend one hundred pieces of gold or to grant titles and rewards to know the enemy's situation, this is the height of inhumanity. Such a general is not worthy of commanding the troops, such an advisor is not worthy of assisting the sovereign, and such a master is not worthy of winning the victory.

故gù明míng君jūn贤xián将jiàng所suǒ以yǐ动dòng而ér胜shèng人rén，成chéng功gōng出chū于yú众zhòng者zhě，先xiān知zhī也yě。先xiān知zhī者zhě，不bù可kě取qǔ于yú鬼guǐ神shén，不bù可kě象xiàng于yú事shì，不bù可kě验yàn于yú度dù，必bì取qǔ于yú人rén，知zhī敌dí之zhī情qíng者zhě也yě。

That is why enlightened rulers and wise generals, who can win and achieve great things that surpass others, do so because they know the enemy's situation in advance. This knowledge cannot be obtained from spirits or gods, nor deduced from events, nor verified by calculations. It must come from men who know the enemy's situation.

故gù用yòng间jiàn有yǒu五wǔ：有yǒu因yīn间jiàn，有yǒu内nèi间jiàn，有yǒu反fǎn间jiàn，有yǒu死sǐ间jiàn，有yǒu生shēng间jiàn。五wǔ间jiàn俱jù起qǐ，莫mò知zhī其qí道dào，是shì谓wèi神shén纪jì，人rén君jūn之zhī宝bǎo也yě。

Therefore, the use of spies has five types: local spies, internal spies, turned spies, dead spies, and living spies. When all five types of spies are employed together, no one can fathom their methods. This is called the divine thread, the sovereign's treasure.

乡xiāng间jiàn者zhě，因yīn其qí乡xiāng人rén而ér用yòng之zhī；内nèi间jiàn者zhě，因yīn其qí官guān人rén而ér用yòng之zhī；反fǎn间jiàn者zhě，因yīn其qí敌dí间jiàn而ér用yòng之zhī；死sǐ间jiàn者zhě，为wèi诳kuáng事shì于yú外wài，令lìng吾wú闻wén知zhī之zhī而ér传chuán于yú敌dí间jiàn也yě；生shēng间jiàn者zhě，反fǎn报bào也yě。

Local spies are recruited from the people of the enemy’s country; internal spies are recruited from the officials of the enemy; turned spies are recruited from the enemy’s spies; dead spies are those who are fed false information to be passed to the enemy; living spies are those who return with information.

故gù三sān军jūn之zhī事shì，莫mò亲qīn于yú间jiàn，赏shǎng莫mò厚hòu于yú间jiàn，事shì莫mò密mì于yú间jiàn，非fēi圣shèng贤xián不bù能néng用yòng间jiàn，非fēi仁rén义yì不bù能néng使shǐ间jiàn，非fēi微wēi妙miào不bù能néng得dé间jiàn之zhī实shí。微wēi哉zāi微wēi哉zāi！无wú所suǒ不bù用yòng间jiàn也yě。

In military matters, nothing is more intimate than spies, no reward is more generous than that given to spies, and no business is more secret than that of spies. Only a wise and virtuous man can use spies, and only a benevolent and just man can employ them. Without great subtlety, one cannot obtain reliable information from spies. Subtle, oh subtle is the use of spies! There is no limit to their employment.

间jiàn事shì未wèi发fā而ér先xiān闻wén者zhě，间jiàn与yǔ所suǒ告gào者zhě兼jiān死sǐ。

If a spy’s mission is discovered before it is executed, the spy and the person who revealed him must be put to death.

凡fán军jūn之zhī所suǒ欲yù击jī，城chéng之zhī所suǒ欲yù攻gōng，人rén之zhī所suǒ欲yù杀shā，必bì先xiān知zhī其qí守shǒu将jiàng、左zuǒ右yòu、谒yè者zhě、门mén者zhě、舍shè人rén之zhī姓xìng名míng，令lìng吾wú间jiàn必bì索suǒ知zhī之zhī。

In all cases where an army is to be attacked, a city is to be taken, or a person is to be killed, it is important to know the names of the commanding officers, the assistant officers, the door-keepers, and the guards. Our spies must seek this information.

敌dí间jiàn之zhī来lái间jiàn我wǒ者zhě，因yīn而ér利lì之zhī，导dǎo而ér舍shě之zhī，故gù反fǎn间jiàn可kě得dé而ér用yòng也yě；因yīn是shì而ér知zhī之zhī，故gù乡xiāng间jiàn、内nèi间jiàn可kě得dé而ér使shǐ也yě；因yīn是shì而ér知zhī之zhī，故gù死sǐ间jiàn为wéi诳kuáng事shì，可kě使shǐ告gào敌dí；因yīn是shì而ér知zhī之zhī，故gù生shēng间jiàn可kě使shǐ如rú期qī。

When an enemy spy comes to spy on us, we should use advantages to seduce him and guide him to become a turned spy. By this means, we can obtain and use turned spies; by this means, we can recruit and employ local and internal spies; by this means, we can feed false information to dead spies to be passed to the enemy; by this means, we can ensure that living spies return at the appointed time.

五wǔ间jiàn之zhī事shì，主zhǔ必bì知zhī之zhī，知zhī之zhī必bì在zài于yú反fǎn间jiàn，故gù反fǎn间jiàn不bù可kě不bù厚hòu也yě。

The sovereign must know the affairs of all five types of spies, and the key to this is the turned spy. Therefore, turned spies must be treated with the greatest generosity.

昔xī殷yīn之zhī兴xīng也yě，伊yī挚zhì在zài夏xià；周zhōu之zhī兴xīng也yě，吕lǚ牙yá在zài殷yīn。故gù明míng君jūn贤xián将jiàng，能néng以yǐ上shàng智zhì为wéi间jiàn者zhě，必bì成chéng大dà功gōng。此cǐ兵bīng之zhī要yào，三sān军jūn之zhī所suǒ恃shì而ér动dòng也yě。

In ancient times, Yi Zhi served Xia before Yin arose, and Lü Ya served Yin before Zhou arose. Therefore, enlightened rulers and wise generals who use intelligent men as spies will achieve great things. This is the essence of war, the basis on which the army moves.