We Know All interrogation techniques
Dependent on thorough preparation and supporting intelligence analysis, the We Know All interrogation techniques can be extremely effective. An ideal candidate for the technique is in a state of shock or fear, such as when initially captured, or naive about what the questioners really can know. This was the main technique of German Luftwaffe interrogators in the Second World War, under the direction of Hans Scharff, who, even in a computer-free time, had extensive databases on Allied air force operations, so was prepared to confront a newly captured prisoner with details about his base, unit, and specific mission. Scharff made extensive use of biographical and order of battle intelligence.
In U.S. doctrine, the interrogator, at the first session, asks pertinent and nonpertinent questions from a list for which the answers are known. If the subject "hesitates, refuses to answer, provides an incomplete response, or an incorrect response, the interrogator himself supplies the detailed answer." A skilled interrogator persuades the prisoner, based on known information, that his answers are really not needed, inducing a sense of futility. Eventually, when the prisoner is conditioned to answer questions, the interrogator begins to introduce those questions for which the answer is not known. The serious questions must still be interspersed with questions to which the answers are known, so the subject can be challenged if he lies. "
The basic technique is noncoercive. Scharff was remembered fondly by many of his prisoners. Sedgwick Tourison, an extremely effective U.S. interrogator in the Vietnam War, would often start with social conversation, inquiring about family, neighbors, and friends. 
- The Interrogator: The Story of Hans Joachim Scharff: Master Interrogator of the Luftwaffe, Schiffer Publishing, Ltd., 1997, ISBN 0764302612
- , Appendix H: Approaches, Field Manual (FM) 34-52: Intelligence Interrogation, U.S. Army, 8 May 1987
- Tourison, Sedgwick Jr. (1990). Conversations with Victor Charlie: an Interrogator's Story. Ballantine Books. ISBN 0804107262.