01The value of prior knowledge先知
孙子曰：
凡兴师十万，出征千里，百姓之费，公家之奉，日费千金；
孙子说：
通常兴兵十万，出征千里，百姓的耗费，国家的开支，每天至少耗资千金；
Sun Tzu said:
Generally, in war, when an army of a 100,000 is raised and sent on an expedition thousands of miles away, the cost to the people and the state is at least 2,000 ounces of gold per day.
内外骚动，怠于道路，不得操事者，七十万家。
国家内外动荡，民夫兵卒因往来奔波而疲惫不堪，不能安心从事耕作的人多达七十万家。
The nation's internal and external turmoil causes 700,000 of civilian families' laborers and soldiers to be exhausted from constant travel, unable to settle down and engage in farming.
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，
战争双方相持数年，是为了争夺最终的胜利，然而（如果将领）吝惜爵位、俸禄和金钱，不肯用它们来了解敌人的情况，那就是不仁到了极点。
Both sides are locked in a protracted struggle for years, aiming for ultimate victory. Yet if rulers and stingy generals with titles, salaries, and money, unwilling to use them to understand the enemy situation, it would be the utmost lack of benevolence.
非人之将也，非主之佐也，非胜之主也。
这样的人不配做军队的将领，不是国君的好助手，也不是能赢得胜利的主宰者。
Such a person is not fit to command an army; he cannot be a good assistant to his sovereign or one who can secure victory.
故明君贤将，所以动而胜人，成功出于众者，先知也。
所以明智的国君、贤能的将领，之所以一出兵就能战胜敌人，成就的功业超越众人，就在于他们能够预先了解敌情。
Therefore, wise rulers and capable generals achieve victory upon taking up arms and surpass others in their accomplishments because they can obtain prior knowledge about the enemy.
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。
要事先了解敌情，不可用祈求鬼神去获取，不可用相似的事情做类比推测，也不可用观察日月星辰运行的度数去验证，一定要从人那里，从那些真正了解敌人情况的人那里去获得。
To gain such prior knowledge does not come from seeking divine assistance through prayer or divination; nor can it be inferred by analogies or verified by observing celestial phenomena. It must be obtained from human sources—specifically those who truly know the enemy situation.
02Five kinds of spies五间
故用间有五：有因间，有内间，有反间，有死间，有生间。
所以使用间谍有五种方式：有因间，有内间，有反间，有死间，有生间。
Therefore, there are five types of spies to be employed: local spies, internal spies, converted spies, doomed spies, and surviving spies.
五间俱起，莫知其道，是谓神纪，人君之宝也。
五种间谍同时使用起来，使敌人无法摸清我军的用间规律，这就是奇妙的方法，是国君克敌制胜的法宝。
When all five types of spies are used simultaneously, and the enemy is unable to discern the pattern of our espionage operations, this constitutes the extraordinary and subtle method, a treasure of the state and a key to victory over the enemy.
因间者，因其乡人而用之。
所谓因间，是指利用敌国乡里的普通人做间谍。
The so-called local spies are those who utilize ordinary people from the enemy's territory as spies.
内间者，因其官人而用之。
所谓内间，是指收买敌国的官吏做间谍。
The so-called internal spies are those who recruit officials from the enemy's ranks as spies.
反间者，因其敌间而用之。
所谓反间，是指收买或利用敌方派来的间谍为我效力。
The so-called converted spies are those who either bribe or manipulate the enemy's spies to work for us.
死间者，为诳事于外，令吾间知之，而传于敌间也。
所谓死间，是指故意散布虚假情况，让我方间谍知道而传给敌方，敌方上当后往往将其处死。
The so-called doomed spies are those who deliberately spread false information known to our spies, which is then relayed to the enemy. Once the enemy is deceived and acts upon this information, these spies are often executed.
生间者，反报也。
所谓生间，是指派往敌方侦察后能活着回报敌情的。
The so-called surviving spies are those sent to gather intelligence from the enemy's territory who are able to return alive with the information.
03Trust & secrecy亲密
故三军之事，莫亲于间，赏莫厚于间，事莫密于间。
所以在军队的事务中，没有比间谍更亲近的人，奖赏没有比间谍更优厚的，事情没有比用间更机密的。
Therefore, in military affairs, there is no one more intimate than the spy, no reward more generous than that given to the spy, and no matter more confidential than the use of spies.
非圣智不能用间，
不是才智过人的将帅不能指挥间谍；
No general of exceptional talent is incapable of employing spies;
非仁义不能使间，
不是仁慈慷慨的将帅也不能驾驭间谍；
No general of exceptional benevolence and generosity is incapable of utilizing spies;
非微妙不能得间之实。
不是用心精细、手段巧妙的将帅不能取得间谍的真实情报。
No general of exceptional meticulousness and ingenuity is incapable of obtaining genuine intelligence from spies.
微哉！微哉！无所不用间也。
微妙啊！微妙啊！真是无处不在用间谍呀！
How profound! How profound! Indeed, there is no end to the use of spies!
间事未发，而先闻者，间与所告者皆死。
间谍的任务尚未施行，就被泄露出去，间谍和知道机密的人都要处死。
The mission of a spy, if prematurely divulged, results in the execution of both the spy and those who are privy to the secret.
04Putting intelligence to work用间
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。
通常，想要攻击敌方军队，想要攻敌方城邑，想要斩杀敌方人员，都必须预先了解那些守城将帅、左右亲信、掌管传达、通报的官员、负责守门的官吏以及门客幕僚的姓名，命令我方间谍一定要侦察清楚。
Generally, if one intends to attack the enemy's army, capture their city, or eliminate their personnel, it is essential to first ascertain the names of those defensive commanders, their close associates, officials in charge of communication and notification, gatekeepers, as well as any retainers and advisors. Orders must be given to our spies to thoroughly investigate these individuals.
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。
一定要搜查出敌方派来侦察我方的间谍，然后利用他，诱导他，放他回去，这样反间就可以为我所用了。
It is essential to apprehend enemy spies sent to reconnoiter our forces. By exploiting them, guiding them, and allowing them to return, we can turn these converted-spies to our advantage.
因是而知之，故乡间、内间可得而使也；
因为有了反间提供的情报信息，了解了敌方的情况，这样乡间（因间）和内间就可以更好地被使用了。
With the intelligence provided by converted-spies, we gain insight into the enemy's situation, thereby enhancing the effectiveness of village spies (local spies) and internal spies.
因是而知之，故死间为诳事，可使告敌。
因为有了反间提供的情报信息，所以散布给死间的虚假情况就可以传给敌方。
With the intelligence provided by converted-spies, false information disseminated by doomed spies can be relayed to the enemy.
因是而知之，故生间可使如期。
因为有了反间提供的情报信息，所以生间就可遵照预定的期限，回来报告敌情。
With the intelligence provided by converted-spies, surviving spies can return within the predetermined timeframe to report on enemy conditions.
五间之事，主必知之，知之必在于反间，
五种间谍使用之事，国君都必须理解，理解的关键在于反间。
The use of these five types of spies is a matter that must be thoroughly understood by the sovereign. The crux of this understanding lies in the effective management of converted-spies.
故反间不可不厚也。
所以，对反间不可不给予优厚的待遇。
Therefore, converted-spies must be granted exceptional rewards and treatment.
昔殷之兴也，伊挚在夏；周之兴也，吕牙在殷。
从前商朝的兴起，在于伊挚曾在夏朝任职；
周朝的兴起，在于姜子牙曾在商朝任职。
（用好间谍可以开创一个王朝）
The rise of the Shang Dynasty can be attributed to Yi Yin's prior service in the Xia Dynasty,
while the rise of the Zhou Dynasty was facilitated by Jiang Ziya's service in the Shang Dynasty.
(Utilizing spies effectively can establish a dynasty.)
故惟明君贤将，能以上智为间者，必成大功。
所以，明智的国君、贤能的将帅，能用极有智谋的人做间谍，一定能成就大的功业。
Therefore, wise rulers and capable generals who employ highly intelligent individuals as spies are bound to achieve great feats.
此兵之要，三军之所恃而动也。
这是战争的关键，整个军队都要依靠间谍提供情报而采取行动。
This is a critical element in warfare, as the entire army relies on the intelligence provided by spies to act decisively.