内外骚动，怠于道路，不得操事者，七十万家。
In addition, there will be continuous commotion both at home and abroad, people will be exhausted by the corvée of transport, and the farm work of seven hundred thousand households will be disrupted.
相守数年，以争一日之胜，而爱爵禄百金，不知敌之情者，不仁之至也，非人之将也，非主之佐也，非胜之主也。
故明君贤将，所以动而胜人，成功出于众者，先知也。
[In ancient times, eight families comprised a community.
When one family sent a man to the army, the remaining seven contributed to its support.
Thus, when an army of one hundred thousand was raised, those unable to attend fully to their own ploughing and sowing amounted to seven hundred thousand households.] Hostile armies confront each other for years in order to struggle for victory in a decisive battle; yet if one who begrudges rank, honours and a few hundred pieces of gold remains ignorant of his enemy's situation, he is completely unaware of the interest of the state and the people.
先知者不可取于鬼神，不可象于事，不可验于度，必取于人，知敌之情者也。
故用间有五：有因间，有内间，有反间，有死间，有生间。
Such a man is no general, no good assistant to his sovereign, and such a sovereign no master of victory.
Now, the reason a brilliant sovereign and a wise general conquer the enemy whenever they move, and their achievements surpass those of ordinary men, is their foreknowledge of the enemy situation.
This 'foreknowledge' cannot be elicited from spirits, nor from gods, nor by analogy with past events, nor by astrologic calculations.
五间俱起，莫知其道，是谓神纪，人君之宝也。
It must be obtained from men who know the enemy situation.
Now, there are five sorts of spies.
These are native spies, internal spies, double spies, doomed spies, and surviving spies.
因间者，因其乡人而用之。
内间者，因其官人而用之。
When all these five types of spies are at work and their operations are clandestine, it is called the 'divine manipulation of threads' and is the treasure of a sovereign.
反间者，因其敌间而用之。
Native spies are those from the enemy's 58 country people whom we employ.
死间者，为诳事于外，令吾间知之，而传于敌间也。
生间者，反报也。
Internal spies are enemy officials whom we employ.
Double spies are enemy spies whom we employ.
Doomed spies are those of our own spies who are deliberately given false information and told to report it to the enemy.
故三军之事，莫亲于间，赏莫厚于间，事莫密于间。
非圣智不能用间，非仁义不能使间，非微妙不能得间之实。
Surviving spies are those who return from the enemy camp to report information.
Of all those in the army close to the commander, none is more intimate than the spies; of all rewards, none more liberal than those given to spies; of all matters, none is more confidential than those relating to spy operations.
He who is not sage and wise, humane and just, cannot use spies.
微哉!微哉!无所不用间也。
And he who is not delicate and subtle cannot get the truth out of them.
Delicate, indeed!
间事未发，而先闻者，间与所告者皆死。
Truly delicate!
There is no place where espionage is not possible.
凡军之所欲击，城之所欲攻，人之所欲杀，必先知其守将、左右、谒者、门者、舍人之姓名，令吾间必索知之。
If plans relating to spy operations are prematurely divulged, the agent and all those to whom he spoke of them should be put to death.
Generally, in the case of armies you wish to strike, cities you wish to attack, and people you wish to assassinate, it is necessary to find out the names of the garrison commander, the aides-de-camp, the ushers, gatekeepers and bodyguards.
必索敌人之间来间我者，因而利之，导而舍之，故反间可得而用也。
You must instruct your spies to ascertain these matters in minute detail.
It is essential to seek out enemy spies who have come to conduct espionage against you and to bribe them to serve you.
Give them instructions and care for them.
因是而知之，故乡间、内间可得而使也；因是而知之，故死间为事可使告敌；因是而知之，故生间可使如期。
Thus, double spies are recruited and used.
It is by means of the double spies that native and internal spies can be recruited and employed.
And it is by this means that the doomed spies, armed with false information, can be sent to convey it to the enemy.
It is by this means also that surviving spies can come back and give information as scheduled.
五间之事，主必知之，知之必在于反间，故反间不可不厚也。
The sovereign must have full knowledge of the activities of the five sorts of spies.
And the key is the skill to use the double spies.
Therefore, it is mandatory that they be treated with the utmost liberality.
昔殷之兴也，伊挚在夏；周之兴也，吕牙在殷。
In old times, the rise of the Shang Dynasty was due to Yi Zhi, who had served under the Xia likewise, and the rise of the Zhou Dynasty was due to Lu Ya, who had served under the Yin.
故惟明君贤将能以上智为间者，必成大功。
And therefore, only the enlightened sovereign and the wise general who are able to use the most intelligent people as spies can achieve great results.
此兵之要，三军之所恃而动也。
Spy operations are essential in war; upon them the army relies to make its every move.