On 24 September 2018, volunteers at the National Museum of Computing at Bletchley Park recreated the process of breaking a message encrypted with the Enigma code used by Nazi Germany during the Second World War. The re-enactment used a reconstruction of one of the electromechanical Bombe devices designed by Alan Turing and Gordon Welchman that moved into a new home in the Park’s Block H earlier this year. The story of the Bombe’s invention, its role in breaking Enigma and the part played by Turing and Welchman has become well known in recent years. What’s less well known, but no less fascinating, is the reason the September event was a live link-up with the World Computer Congress in Poznan (organised by IFIP, the world federation of national computer societies). The demonstration was a belated tribute to the Polish mathematicians who broke Enigma, as well as the British codebreakers who developed their techniques and made such a huge impact on the outcome of the Second World War. The congress was hosted by the Poznan Supercomputing and Networking Centre, which is affiliated to the University of Poznan, where Polish Enigma codebreakers were trained in the early 1930s in clandestine courses. They revealed their work to their British and French allies in 1939, enabling them to start reading Enigma messages as the Second World War began. It was this running start that helped Bletchley Park automate the decryption process to reveal Enigma messages. ‘X, Y & Z’ (The History Press, £20, ISBN 9780750987820) is the first English account of the work of the Polish codebreakers and how instrumental they were in helping decipher the code for Enigma. Written by Alan Turing’s nephew, Sir Dermot Turing, a trustee at Bletchley Park, it acknowledges those pioneering Polish codebreakers whose discoveries, handed over to the UK’s Government Code & Cypher School before war began in 1939, provided the intellectual foundation on which Bletchley Park’s success was built. Without their contribution, the British attack on Enigma would have been delayed by many months, possibly years, with unimaginable consequences. Their story is well overdue for telling to a wider audience, just as Turing’s once was, and ‘X, Y & Z’ is just one part of efforts to recognise the crucial role they played. On 1 September 2018, codebreaker Henryk Zygalski was publicly remembered for the first time when a memorial stone was unveiled at his grave in Chichester cemetery. Zygalski’s personal involvement with Enigma began in about 1933. Later he was instrumental in inventing a scheme for finding the rotor-settings of the Enigma machine using perforated cardboard sheets, named ‘Zygalski Sheets’. Using these, the Allies were able to decipher encrypted German messages in the first months of 1940, at a time when machine-based methods were still untried. Zygalski had escaped from Poland in 1939 and worked with French Secret Intelligence until the total occupation of France in 1942. He then escaped to Britain and worked for Polish Secret Intelligence until after the War. Of the three most famous Polish codebreakers who are the main protaganistis of this book, only Zygalski managed to have a relatively secure post-war life, settling in Britain and becoming a mathematics lecturer at what subsequently became the University of Surrey. Jerzy Rózicki perished in a shipwreck in 1942; Marian Rejewski returned to Poland in 1945 where he was investigated by the Communist-era secret police and limited to uninspiring work. history of technology reviews books volume 13 issue 10 history codebreaking Related stories Mechanical Engineer – Cambridge and Antarctica Cambridge but with periods at sea or in polar regions. Starting from £30,357 per annum. 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