Current Issue

Polish Reconstitution of the German Military
Enigma and the First Decryptments of its Messages
by GILBERT BLOCH -- abstract

In 1928, an adaptation of the “commercial” Enigma went into service for the Reichswehr. The improved 1930 Militär-Enigma was considered to present cryptanalysts with an insoluble problem. Nonetheless, the system did involve provisions liable to jeopardize security, which, in combination with documents furnished by Hans-Thilo Schmidt (HE/Asche) to the French, would eventually enable three brilliant Polish mathematicians to decipher most of the German Army messages between 1933 and 1938. The French, in late 1930, had created Section D of the “Service de Renseignement” under Captain Gustave Bertrand in order to gather information on the enciphering methods use by foreign countries. The following year, the contact with Asche was established. After first attempts had failed to study and use the materials with the British, Bertrand successfully contacted the Poles, who as early as 1929 had set up a special course on cryptology at Poznan University and thereby had brought civilians with extensive mathematical knowledge to bear on the problem. Marian Rejewski, Henryk Zygalski, and Jerzy Rózycki succeeded in the reconstitution of the machine and messages were deciphered, in spite of various changes the Germans introduced. Only in March 1939, after the Germans had added two more rotors to the Enigma, did the flow stop. When the British promised the Poles assistance in time of need, it was the beginning of close cooperation between Poland, France, and Great Britain.