had by then escaped from German-overrun Poland to PC Bruno outside Paris, France. The remaining sheets were completed on 7 January 1940, and were couriered by Alan Turing to France shortly thereafter. "With their help," writes Rejewski, "we continued solving Enigma daily keys." The sheets were used by the Poles to make the first wartime decryption of an Enigma message, on 17 January 1940. In May 1940, the Germans once again completely changed the procedure for enciphering message keys (with the exception of a Norwegian network). As a result, Zygalski's sheets were of no use, though the Herivel tip could still be used. See also Cryptanalysis of the Enigma Bomba ("cryptologic bomb"): machine designed about October 1938 by Marian Rejewski to facilitate the retrieval of Enigma keys Bombe: a machine, inspired by Rejewski's "cryptologic bomb," that was used by British and American cryptologists during World War II Grille (cryptography) Punched card Jacquard loom Notes References A revised and augmented translation of W kręgu enigmy, Warsaw, Książka i Wiedza, 1979, supplemented with appendices by Marian Rejewski and others. Appendix C of Appendix E of External links Javascript demonstration of Zygalski sheets "Polish Enigma Double" About the Enigma (National Security Agency) "The Enigma Code Breach" by Jan Bury The "Enigma" and the Intelligence "Codebreaking and Secret Weapons in World War II" By Bill Momsen A Brief History of Computing Technology, 1930 to 1939 The Daily Telegraph obituary of Mavis Batey https://www.telegraph.co.uk/news/obituaries/military-obituaries/special-forces-obituaries/10447712/Mavis-Batey-obituary.html Cryptographic attacks Science and technology in Poland Cipher Bureau (Poland) Polish inventions Perforation-based computational tools