Intelligence and Espionage,用间 is Chapter 13 of Sun Zi Art of War.

Costs of War by Sun Zi

English: Sun Zi said: Raising an army of 100,000 for a distant military campaign will impose severe strains on the incomes of the people. This, together with the drain on the state treasury, will amount to a daily expenditure of 1000 pieces of gold. There will be great commotion and disruption of peace at home and abroad, and people will be exhausted from transporting military supplies along supply routes. The disruption to work, jobs and various professions will affect 700,000 households.

Modern: 孙子曰：凡兴兵十万，出征千里，百姓的耗费，国家的开支，每天要花费千金；全国上下动荡不安，运输军需物资的队伍疲惫于道路上，不能从事耕作的有七十万家。

Original: 孙子曰：凡兴师十万，出征千里，百姓之费，公家之奉，日费千金；内外骚动，怠于道路，不得操事者，七十万家。

Why Intelligence by Sun Zi

English: Two opposing armies may be at war with each other for many years, seeking the ultimate day of victory. However, if one is reluctant to part with honour and ranks, money and gold for espionage purposes and remains ignorant of the situation of the enemy, he is extremely inhumane. Indeed such a person can never be a general of men, can never be a good assistant to the ruler and can never be a master of victories. Thus, the enlightened ruler and the capable general are able to secure victories for their military campaigns and achieve successes that surpass those of many others. The reason is because of foreknowledge.

Modern: 战争双方相持数年，是为了取胜于一旦，如果吝啬爵禄和金钱不重用间谍，以致不能了解敌情而导致失败，那就是不仁到极点。这样的将帅，不是军队的好将帅，不 是国君的好帮手；这样的国君不是能打胜战的好国君。英明的国君、良好的将帅，之所以一出兵就能战胜敌人，成功地超出众人，就在于事先了解敌情。

Original: 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。

Where to Gather Intelligence by Sun Zi

English: This foreknowledge cannot be obtained from the spirits nor from the gods. It cannot be obtained by comparing with similar present or past events and situations. Neither can it be obtained from the study of astrology. This foreknowledge must be obtained from men who have knowledge of the situation of the enemy.

Modern: 要事先了解敌情，并非祈求鬼神取得，并非用相似的事做推测，也并非观察日月星辰运行来验证，而是取于了解敌情的人。

Original: 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。

Types of Spies by Sun Zi

English: There are five kinds of secret agents that can be used. They are local agents, inside agents, double agents, doomed agents and live agents. When these five types of agents are deployed simultaneously, their complex modes of operations will be beyond comprehension of the enemy. They are like mythical and divine schemes that can be deemed the most precious treasures and weapons of the ruler.

Modern: 使用间谍有五种：有因间，有内间，有反间，有死间，有生间。物种间谍都用起来，能使敌人不知道我方用间的规律，这是它神妙之处，国君胜敌的法宝。

Original: 故用间有五：有因间，有内间，有反间，有死间，有生间。五间俱起，莫知其道，是谓神纪，人君之宝也。

Descriptions of Spies by Sun Zi

English: Local agents are ordinary people recruited from the homeland of the enemy and used as spies by us. Inside agents are officials of the enemy who are recruited and employed by us. Double agents are spies of the enemy who have been recruited to work for us. Doomed agents refer to our own spies who are unable to keep secrets and are then deliberately fed with false information to leak to the spies of the enemy. Living agents are our spies who have returned safely from the territory of the enemy with information.

Modern: 利用敌国乡里的普通人作间谍，称作为因间；收买敌国官吏做间谍，称作为内间；收买或利用敌方所派来的间谍，称作为反间；故意散布假情报，使我方间谍知道，然后传给敌方敌人上当后将间谍处死，称作为死间；派往敌方侦查后能活着回来报告敌情的人，称作为生间。

Original: 因间者，因其乡人而用之。内间者， 因其官人而用之。反间者，因其敌间而用之。死间者，为谈事于外，令吾间知之，而传于敌间也。生间者，反报也。

Relationship with Spies by Sun Zi

English: Thus, among all military relationships, none can be more intimate that that maintained with spies and secret agents. There can be no bigger rewards than those showered on spies and secret agents. There can be no greater secretive operations than those pertaining to espionage.

Modern: 所以在军队人事中，没有比间谍更亲信，奖赏没有比间谍更优厚，事情没有比使用间谍更机密。

Original: 故三军之事，莫亲于间，赏莫厚于间，事莫密于间。

Who & Where to Use Spies by Sun Zi

English: Only those who are wise will be able to use secret agents. Only those who are benevolent, loyal and just are able to deploy and use secret agents. Only those who are thorough and detailed will be able to decipher the truth embedded in espionage reports. Such is the intricacy and subtlety of espionage. Indeed, there is no place where espionage cannot be used.

Modern: 不是才智过人的人不能使用间谍，不是仁慈慷慨的人不能用间，不是用心微妙的人不能取得间谍真实的情报。微妙！真是无所不可使用间谍。

Original: 非圣智不能用间，非仁义不能使间，非微妙不能得间之实。 微哉微哉！无所不用间也。

When Espionage Activities Leak by Sun Zi

English: When espionage activities and secret operations have been leaked before their implementation, then the agents concerned and those whom they are in contact with must be put to death.

Modern: 用间的计谋尚未实施，就被泄漏出去，间谍和知道机密的人都要处死。

Original: : 间事未发而先闻者，间与所告者皆死。

Seeking Information by Sun Zi

English: There may be army you wish to strike, cities you wish to conquer and key people you with to assassinate.For such cases, there is a need to know beforehand detailed information on the identities of the garrison commander, his supporting officers, the visiting consultants, the guards and patrols, and various attendants. Your agents must be ordered to investigate these matters in great detail.

Modern: 凡是要攻击的敌军，要攻取的城邑，要刺杀的敌方官员，必须先了解那些守城将官、左右亲信、掌管传达通报的官员、守门官吏和宫中近侍官员等姓名，指令我方间谍一定要侦查清楚。

Original: 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，令吾间必素知之。

Creating Double Agents by Sun Zi

English: The secret agents of the enemy who are spying among us must be actively sought out. Use incentives to bribe them, guide and counsel them and them pardon and release them. Thus they can become double agents and be used and employed by us.

Modern: 必须搜查出前来我方侦查的敌军间谍，依据情况用重金收买，优利款待，然后放他回去，这样反间就可以为我所用。

Original: 必素敌间之来间我者，因而利之，导而舍之，故反间可得而用也。

Importance of Double Agents by Sun Zi

English: It is through information gained from double agents that the situations of the enemy can be known, and loyal and inside agents can be recruited and deployed as well. It is through the intelligence gained from the double agents that we are able to use doomed agents to carry false information to the enemy. It is through the efforts of the double agents that our living agents are able to return on time with important reports of the enemy. The ruler must know fully how to use and operate the five different kinds of agents and espionage activities. However to know the situation and condition of the enemy, the ruler must depend on double agents. Thus double agents must be treated the most generously.

Modern: 通过反间了解敌情，这样乡间、内间就可以为我所用了；通过反间了解敌情，这样就能使死间把虚假情报传给敌人；通过反间了解敌情，这样就可以使生间按预定时 间，回来报告敌情。五种间谍的使用，国君都必须掌握，而要了解敌情的主要关键在于使用反间，所以反间不可不给予优厚的待遇。

Original: 因是而知之，故乡间、内间可得而使也； 因是而知之，故死间为诳事，可使告敌。因是而知之，故生间可使如期。五间之事，主必知之，知之必在于反间，故反间不可不厚也。

Espionage & Victory by Sun Zi

English: In ancient times, the rise of the Shang Dynasty over the Xia Dynasty was because its military advisor Yi Yin, had served as an official in the kingdom of Xia. Similarly, the rise of the Zhou Dynasty over the Yin Dynasty was because its military advisor, Lu Ya, had served as an official in the kingdom of Yin. Thus, it is the enlightened ruler and the capable general who are able to use the most intelligent ones from within their ranks to be deployed as spies and secret agents so as to achieve the greatest and complete victories in war. Secret operations and espionage activities form an integral part of any military campaign as the planning of strategies and the movement of troops depend heavily on them.

Modern: 从前商朝的兴起，是因为重用了曾经在夏为臣的伊尹；周朝的兴起，是因为重用了在殷为官的姜子牙。所以，明智的国君、贤能的将帅，能用高超智慧的人做间谍，一定能成就大业。这是用兵作战重要的一着，整个军队都要依靠他提供情报来采取行动。

Original: 昔殷之兴也，伊挚在夏；周之兴也，吕牙在殷。故明君贤将，能以上智为间者，必成大功。此兵之要，三军所恃而动也。

Sumber : http://www.chinese-wiki.com/Sun_Tzu_Art_of_War_Chapter_13