GUPPY aimed to modernize American submarines, starting with reverse engineering German Type XXI U-boats. -The program, which ran from 1947 to 1963, included multiple iterations, such as GUPPY I ...

Say hello to the Navy’s GUPPY submarine program of the early ... the testing and reverse engineering of two Nazi German Kriegsmarine Type XXI U-boats, which had been surrendered to the Americans ...

German forces in Denmark had surrendered ... Type XXI U-boats and used them to developed their own submarine technology. The Type XXI design inspired the Soviet Union Whiskey-class and the U.S ...