Hanns Scharff was an interrogator for the Luftwaffe during World War II. Eschewing violence, his methods were so successful that the United States began teaching them during the post war period.
From the wiki:
After a prisoner's fear had calmed, Scharff continued to act as a good friend to the prisoner, including sharing jokes, homemade food items, and occasionally alcoholic beverages. Scharff was fluent in English and knowledgeable about British customs and some American, which helped him to gain the trust and friendship of many of his prisoners. Some high profile prisoners were treated to outings to German airfields (one POW was allowed to take a German aircraft for a trial run), tea with German fighter aces, swimming pool excursions, and luncheons among other things. Prisoners were treated well medically at the nearby Hone Mark Hospital, and some POWs were occasionally taken from captivity to visit their comrades at this hospital for company's sake as well as the better meals provided there. Scharff was best known for taking his prisoners on strolls through nearby woods, first having them swear an oath of honor that they would not attempt an escape during their walk. Scharff chose not to use these nature walks as a time to directly ask his prisoners obvious military-related questions, but instead relied on the POWs' desire to speak to anyone outside of isolated captivity about informal, generalized topics. Prisoners often volunteered information the Luftwaffe had instructed Scharff to acquire, frequently without realizing they had done so.
