Sir Martin writes:
On 25 and 26 July 1939, five weeks before the outbreak of the Second World War – and while Churchill was still in opposition to the government of the day, in his tenth year in the political wilderness – senior Polish Intelligence officers in Warsaw handed over to a British Intelligence Mission then in Poland their latest model of a reconstructed German cypher machine, the Enigma machine. The British representatives were astonished to see not only Enigma replicas, but also a machine, called by the Poles a ‘Bomba’, that could break the Enigma settings.
Possession by Britain of the reconstructed Enigma machine and the Bomba meant that top-secret German radio signals, easy to pick up by radio receiving stations in Britain and elsewhere in their cyphered form, could then, after a massive effort of the codebreaking skill, be decrypted. Building on the Polish Bomba, two mathematicians at Bletchley, Gordon Welchman and Alan Turing, designed and built a more advanced cryptanalytic machine, known as a Bombe: the first Bombe to be operational arrived at Bletchley Park in August 1941.
The techniques of decryption of the daily changing Enigma cyphers were incredibly hard. But by building up a staff of more than five thousand cryptographers, analysts and Intelligence experts, Britain’s Government Code and Cypher and School, the main site of which was at Bletchley Park, Buckinghamshire, forty-three miles north-west of London, was able to break at least half of the five hundred German Enigma circuits – or ‘keys’ as they were known. Churchill later called these decrypts his “golden eggs”. They had been laid, he commented, by “the geese who never cackled” – the Bletchley Park staff whose maintenance of the strictest secrecy protected their “golden eggs” – more than half a million Enigma messages in all – throughout the war.
To receive Book Club discounts and read Sir Martin’s personal reflections and news: Subscribe to Sir Martin’s Newsletter & Book Club
Follow and share Sir Martin on Twitter @ SirMartin36 and Facebook Sir Martin Gilbert