The Storm of War - Andrew Roberts [198]
For those who would prefer other explanations to divine intervention, the story of the cracking of the Enigma machine is also full of secular miracles. The design was patented by a Dutchman, H. A. Koch, in 1919, and by 1929 had been bought by the German Army and Navy (which used different versions of it). Looking like a normal typewriter but with three, four or five twenty-six-spoke rotor wheels attached, as well as lights and plugs that resembled a telephonist’s board, the machine had the ability to transform a typed message into a code so complicated that the Germans assumed it could never be broken. ‘To give an idea of how secure these machines are,’ General Franco’s intelligence officer Commander Antonio Sarmiento wrote in a 1936 report, when the Nationalists were buying ten Enigma machines from the Germans at the start of the Spanish Civil War, ‘suffice to say that the number of combinations is a remarkable 1,252,962,387,456.’4
The technical side of the Enigma story is ferociously complex, and involves specialist terms such as the Banburismus procedure, Caesar reflector, Dolphin, Porpoise, Shark and Triton nets (that is, sub-codes), the Eins catalogue, Cillis, the Herivel Tip, codes-within-the-code, Gamma wheels, perforated sheets and plugboard connections, rodding, Bigram tables, bombes, cross-ruffing, straight-cribs and a related code entitled Geheimschreiber (secret writer).5 The cracking of Enigma and its related codes – such as the Japanese diplomatic cipher Purple which was transformed into decrypts codenamed Magic – was a genuine Allied operation, involving the secret services of Poland, France, Britain, Australia and the United States. It began as early as 8 November 1931, when a traitor working in the German Cipher Office called Hans Thilo Schmidt allowed the French Deuxième Bureau (secret service) to photograph the Enigma operating manuals, which he had momentarily spirited out of a safe in the War Ministry. The French told the British, who subsequently told the Poles about the machine, but none could crack the code without building a replica of the machine itself. This was achieved by the Polish cryptographer Marian Rejewski in December 1932, although the Poles did not initially inform the French and British that this had happened. From that point on, the Poles could read Wehrmacht and Kriegsmarine radio traffic, although when in 1937 the latter changed its Enigma indicating key (the setting on a vital cog) the naval side fell silent, and was to remain so for the next three crucial years. Changes in the machines instituted by the Germans in December 1938 (installing an extra two rotor wheels, bringing the total to five) and January 1939 (doubling the number of plugboard sockets) also plunged the Poles into darkness. In late July 1939 they finally told the French and British secret services that they had been reading the German traffic until late 1938.
Ultra was not the sole means by which the Allies gathered intelligence, of course. Prisoners were captured and interrogated; simpler signals intelligence (sigint) codes used by front-line communications were eavesdropped upon and decoded by a British organization known as the Y Department; aerial photo-reconnaissance was interpreted at Medmenham on the Thames; resistance groups in Occupied Europe passed on information; SIS produced human intelligence (humint) from its own sources, although many were compromised early on in the