The Secrets of Room 40

By Roger Davies / 12 October 2013 / History, In the News, Technology

Some of Edward Snowden’s efforts have disclosed some of the intelligence agencies’ advanced technical capabilities in terms of communications interception. I’m not going to make a judgment call on that here.  However, let’s look at similar advanced communications intelligence technical capabilities in history, and maybe draw some parallels:

Room 40 and the Zimmerman Telegram.   In 1917 British Naval intelligence signals intelligence operated out of Room 40 in the Admiralty Building. Think of Room 40 as the WW1 equivalent of Bletchley Park. They had developed the capability to intercept and decode telegrams. Indeed just about every telegram that went across the Atlantic and every radio message was intercepted.  In January 1917 they intercepted the notorious “Zimmerman telegram” from German High Command to the German ambassador in Mexico. Intercepting and decoding this telegram had significant effects on the outcome of WW1, showing the American government and people the true nature of the German strategy, and its efforts to encourage Mexico to attack the USA. Even when the telegram was ‘leaked” significant efforts were made to hide the method by which the signal was intercepted and decoded.

If the equivalent of Edward Snowden had been operating prior to 1917, and had leaked the British technical capability to intercept and de-crypt in this field, the telegram would not have been intercepted and the outcome of the war may have changed, with negative effect on the UK.

Enigma and Dilly Knox. One of the decryption experts during WW1 in Room 40 was an academic called “Dilly” Knox.   Mr Knox was a remarkable man and had influence on the British signals intelligence decoding capability probably much more than the more famous Alan Turing. In the 1920’s and 1930s he was again working for the British government developed mechanisms for decoding “Enigma” messages, as early as the mid 1920’s, to some degree. Turing’s early computers applied techniques that Dilly Knox had developed.

If an equivalent of Edward Snowden had disclosed the British code-breakers capability to the Germans in the mid 1930’s, I wonder who would have won WW2?


The Zimmermann De-cryption
The Zimmermann De-cryption



The exploits of Knox and his colleagues in Room 40 are remarkable, fascinating and deserve (now!) significant attention. We should be glad, of course, that their secrets and capabilities stayed secret.

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