World War II Communications:
European Decoding of Nazi Messages

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[Bury]

Modern Enigma

" In May 1941, the German submarine U-110 attacked a convoy near Greenland.  A counterattack by the British destroyer Bulldog forced the sub to the surface, where the crew abandoned it." [Rogers]  The German crew left a great deal of explosives within the U-boat, but they did not explode.  The British troops from the Bulldog were able to go into the German submarine and discovered the enigma machine along with many vital code books.

[Bury]

Pictures of various Enigmas used to decode the German messages.

Though having the Enigma and code books gave the Allied powers a great advantage, it simply was not enough.  "The British still had to figure out how to recognize quickly when the settings of a German enigma had been changed and what the new settings were.  Their answer, to which Turing made major contributions, was the 'Bombe', the first of several machines that worked by matching the electrical circuits of Enigma." [Rogers]. The 'Bombe' proved to be an essential key in breaking the German codes and it's creation became a pivotal point within the war.

[Debrowa]

In order from left to right: "Capt. H. Braquenie, Col. G. Bertrand, A. Denniston, A.D. Knox, Gen. Sir S. Menzies, Marian Rejewski, Jerzy Rozycki and Henryk Zygalski" [Debrowa]

These men were some of the cryptologists and military men put in charge of the Enigma and cracking it's code. Men like, Marian Rejewski, Jerzy Rozycki and Henryk Zygalski received medals for their efforts and contributions to the war effort. The Poles were able to break the Enigma code after the 'Bombe' had been created quite often, making it quite easy to decrypt the messages.  Around 1937 the codes began to change and in 1938 German messages had become unbreakable once again. "Polish intelligence agents in Germany found that the Germans were changing the initial rotor positions not once a day but with every message so the existing methods were no longer adequate." [Debrowa] Marian Rejewski set to fix this problem immediately. He invented a machine, consisting of 6 'Bombes' making it the fastest decoding resource out there. 

Another man, H. Zygalski, developed a method using 51 X 51 perforated sheets of paper. This new development made the 'Bombe' of lesser demand and the codes become decryptable quicker and more easily.

[Debrowa][Kahn]

Left: One of the sheets used in Zygalski's method. Right: "Enchipherment table H-1 for a digraphic cipher of an R.S.H.A. radio net in Norway." [Kahn]

Just as the Polish begn to perfect their decrypting methods the Germans added two new rotor wheels, making the codes harder to decrypt. With the amount of time and resources growing thin Gen. W. Stachewicz, Cheif of Staff, decided to turn over all of their methods and know-how to the British and France. This action had to be done in the greatest secrecy.

"A conference was set for 25-27 July 1939 to which the French and the British crypto specialists were invited. The conference participants representing France, Britain and Poland were as follows -

From France, Colonel G. Bertrand (radio intelligence) and Captain H. Braquenie (intelligence)

From Britain, Colonel S. Menzies (Chief of British Intelligence), A. Denniston (Chief of G.C.C.S.) and A.D. Knox (cryptologist from G.C.C.S.)

From Poland, Colonel G. Langer (Chief of Cryptology), Major M. Ciezki (Chief of the German section, BS4), M. Rejewski, J. Rozycki and H. Zygalski (cryptologists), A. Palluth (mechanical engineer from AVA) and C. Betlewski (mechanical engineer from AVA)." [Debrowa]

At the conference Zygalski and Rejewski each explained their methods to the British and French specialists, effectively educating the very people who would work to defeat the Nazi powers.