A pair of historic Enigma machines used during the Spanish Civil War have been donated to Britain.
The machines played a role in an untold chapter of British wartime code-breaking history: the early 20th-century kit encoded messages that, once intercepted, helped boffins crack German military encryption at Bletchley Park in the Second World War.
When Hitler and Mussolini sent troops to fight alongside Franco's Spanish nationalists during the civil war in the 1930s, the Germans used sets of commercially available albeit modified Enigma machines to establish secure communications with their Condor Legion.
Britain had purchased an off-the-shelf Enigma machine in 1927 - and although the nation's top experts understood how it worked, they had no opportunity to break Hitler's encrypted messages because the German military's signals didn't reach Britain, BBC News reports.
However Enigma-encoded communications sent by the German Condor Legion in Spain could be overheard, allowing pioneering British codebreaker Dilly Knox to begin work on decryption tactics. After months of painstaking effort Knox successfully cracked the first Enigma message in April 1937.
The military machines used years later by the Wehrmacht during World War II featured a plugboard that added an extra layer of complexity and made the gear, at first, unbreakable.
Prior to the Second World War the Poles were intercepting German message traffic and had started developing mathematical approaches towards cracking it. The Poles shared their work with British code-breakers, including Knox, in a meeting brokered by the French just prior to the outbreak of World War II.
This intelligence gave boffins at Bletchley Park a start on cracking military Enigma machines, although they were already aided by Knox's earlier work on the Spanish Enigmas' messages.
"It gave them the foundations and it gave them the confidence that however more complicated the German military Enigma was - and in particular the German Naval Enigma - it was a resolvable problem," explained Tony (who declines to give his last name), an historian at UK snooping centre GCHQ. "It was something that would not defeat them."
Stumbled upon by chance
The Spanish Enigmas donated to Britain were among two dozen discovered by chance by a non-commissioned officer in a secret room at the Spanish Ministry of Defence in Madrid a few years ago.
"Nobody entered there because it was very secret," explained Felix Sanz, the director of Spain's intelligence service, BBC News reports.
"And one day somebody said: 'Well if it is so secret, perhaps there is something secret inside.' They entered and saw a small office where all the encryption was produced during not only the civil war but in the years right afterwards."
After learning of the discovery, Tony got in touch with Spanish counterparts asking if it might be possible to obtain some of the machines. Following lengthy negotiations the Spanish agreed to hand over two machines. One will be held at GCHQ while another will go to Bletchley Park, where it will be put on public display.
In return, the British donated a German four-rotor Naval Enigma machine to the Spanish. It's hoped the machines could form the foundations for a display on code-making and code-breaking at the Spanish Army Museum, in Toledo, where the handover ceremony took place last Thursday. ®