The code-breakers you don't know

The contribution made by the Government Code and Cypher School at Bletchley Park is well documented, but its First World War precursor has received much less attention.

Paul Gannon’s newly-published book ‘Inside Room 40’ examines the activities of the code breaking class of 1916 housed in the eponymous quarters at the Admiralty in London, and reveals how even by the comparatively wiretapping techniques of the day, the intelligence it gathered and disseminated aided allied operations both on the European fronts and beyond.

A global wired telegraph network was long established by the outbreak of the conflict, alongside as wireless telegraphy transmission, and the warring nations were soon reliant on these for the transmission of all kinds of communications, military logistical, and diplomatic. With telegraphy, however, most major wire routes were openly commercial, and open to interception by the national authorities whose territory they crossed – giving the British a major strategic advantage in that the British Isles was something of a communications hub for telegraph traffic.

German secret messages were perforce sent coded, and the British showed perspicacity in setting-up a taskforce dedicated to breaking these codes and ciphers, and ensuring that the intelligence thus gathered was (in most cases) quickly conveyed to relevant parties in the armed forces and elsewhere where they would bring strategic advantage. As with Bletchley Park more than two decades later, the individuals who staffed Room 40 were recruited for their analytical acumen as much as their language skills, and Gannon profiles they key members of this eclectic – and at times eccentric – team. It included moneyed wireless technology enthusiasts and linguists, as well as mathematicians and analytical specialists.

As with their Second World War inheritors, luck played a decisive part in Room 40’s occupants’ successes, particularly with German codebooks being captured or falling into allied hands, often without the Germans themselves being aware of it. The most significant example of this was the so-called ‘Zimmermann telegram’ that the Room 40 team decoded, and leaked to Washington in 1917. This contained a proposal from Germany to Mexico enjoin with them in declaring war on the US, and was a decisive factor in persuading President Woodrow Wilson to approve his country’s entry into the hostilities.

Extant knowledge of Room 40’s work is curtailed by the fact that much documentation was destroyed during or after its period of operation; however, it is known that Room 40’s remit took it into what now would be called the ‘cutting edge’ of code breaking technology. Possibly the most intriguing part of Gannon’s finds in Room 40 files at the National Archives is that it devised some manner of code-breaking machinery; this challenges the common perception that the Colossus and Bombe of Bletchley Park (the subject of Gannon’s previous history) constituted the origins of mechanised – and indeed computerised – code cracking. The details of Room 40’s machine are tantalisingly scarce. Gannon speculates on what form it might have taken, the most likely being some kind of punched card apparatus which, nonetheless, could lay claim to performing as a primitive computer of sorts.

A breakthrough aspect of wireless technology given impetus by Room 40 was direction finding, which deployed sensitive receivers and aerials which could be used to indicate the direction from which a wireless signal was being transmitted. Two (or more) direction finding stations would allow the drawing of compass bearing on a  map and the points where the lines crossed would indicate roughly a transmitters location. This techniques, developed by Marconi Company staffer Captain HJ Round, not only helped establish a ‘picture’ of German transmitting capability – and thereby a picture of the German order of battle – but later also provided a limited degree of warning of German air attacks on the British mainland. 

Room 40 was disbanded a year after the war’s end, and its function merged with the British Army's intelligence unit MI1b to form the Government Code and Cypher School, later housed at Bletchley Park; the fact that some of its key figures went on to work there ensured that its legacy spanned the two conflicts
‘Inside Room 40’ is published by Ian Allan Publishing at £19.99.

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