The German investigation triggered by the revelation of the leaked meeting with Hitler had been ongoing since the end of 1938. From the autumn of 1939, it was accompanied by the ‘Fall Wicher’ investigation examining the possibility that the German ciphers had been broken by the Polish cryptology service. Both seem to have found a common end with the revelation of Hans-Thilo Schmidt’s treachery and the interrogation of the heads of the former Polish Cipher Bureau at Castle Eisenberg. The issue of information leakage at the highest levels of the Third Reich was cleared up and, in the process, the security of the Enigma ciphers was confirmed. Despite this, historians and cryptologists alike are still debating how it was possible that the succeful attack at the Enigma ciphers, initiated in 1932 and carried out on a large scale since the outbreak of the war, did not come to the attention of German cryptologists, the Third Reich’s intelligence service or the services using the machine? Any competent cryptologic service, and at least some of the German services in this area could not be denied competence, constantly analyses the security of its own communications, thoroughly investigating any events indicating even a slight probability of a breach. Why, in nearly 20 years of operational use of the machine, did none of its users notice the facts whose genesis could most easily be explained by the breaking of the cipher? Why did none of the cryptology agencies, which began employing mathematicians en masse at the outbreak of war, identify weaknesses in Enigma’s design or use? Were the Allied measures taken to protect the secret so successful, or were the German cryptologists and intelligence services so ineffective?