What did Stevenson write about concerning Germany and how does he have access to the German communication network?

The Americans were making some efforts to break Japanese code; the information they had came from Colonel Bill Donovan who functioned in the same capacity for Roosevelt as Stevenson did for Churchill. Both Stevenson and Donovan agreed about the danger posed by Hitler and Germany. Their German counterpart at this time was Reinhard Heydrich who worked closely with his father-in-law, Admiral Wilhelm Canaris, who was involved with German foreign intelligence.