The most skilled Nazi Germany interrogator was never tried for war crimes, but actually invited to speak to the US military about his techniques!

Hanns-Joachim Schraff was the greatest German interrogator during World War II. He was so skilled that he was nicknames “The Master” by his peers. He primarily worked with US airmen to extract information from them. His big secret was the fact that he was a very humane man who used kindness and respect for human dignity on everyone he interrogated. 

Schraff realized only a fraction of his captives would have any vital information for coming attacks and that torture would only increase the likelihood of false information. Instead, Schraff made his captives as comfortable and relaxed as possible. He would speak of philosophy and other safe topics with his captives and slowly piece together bits of information from them. He was German’s best interrogator and he never even raised his voice. 

Schraff wasn’t tried for war crimes when World War II was over, due to his commendable humanity shown to his prisoners. Instead, he was invited by the US military to share his techniques. To this day his techniques are taught and used worldwide. 

(Source)