Heeresversuchsanstalt Peenemünde
Adolf Hitler did not fully trust Fellgiebel; Hitler considered him too independent-minded, but Hitler needed Fellgiebel's expertise. Fellgiebel was one of the first to understand that the German military should adopt and use the Enigma encryption machine. As head of Hitler's signal services, Fellgiebel knew every military secret, including Wernher von Braun's rocketry work at the Peenemünde Army Research Center.