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Before Bletchley Park

The Codebreakers of the First World War



Paul Gannon

Cheltenham, Gloucestershire UK: History Press, 2022.

Paperback   352pp   RRP $37.99


Reviewer: Neville Taylor, May 2023


Paul Gannon provides an excellent account of Britain’s use of intercepted traffic of other nations both before and during the First World War. Submarine cables were the first source of this intelligence – usually with a view to gaining a political or commercial advantage. It was not until the first decade of the 20th century that the use of radios became prevalent. In 1914 Britain was fortuitously at a Marconi promotion in Germany, and hence had access to the location of all their global wireless stations for their naval and commercial fleets. Excellent maps have been provided of their world network, and in particular those on the African continent.

With war being imminent, Britain set about severing any undersea cables that Germany used, including the trans-Atlantic link to New York. When war was declared, British forces wiped out as many international transmitting stations as possible – most of these were on the coastline, so were easy ‘prey’. On 11 September 1914 the Australian Naval and Military Expeditionary Force captured the German asset at Rabaul before the convoys of troops sailed for ‘the Western Front’. On 9 November 1914, HMAS Sydney, escorting the first convoy, sank the SMS Emden heading to destroy the cable and wireless station on Direction Island in the Cocos Islands group.

In August 1914 wireless messages illegally intercepted by amateur enthusiasts were being sent to the Admiralty, where they piled up on the desk of the Director of Naval Intelligence, Henry Oliver. He had no free staff, let alone any with the possible capability of deciphering what seemed to be a valuable information source. Oliver offered Sir Alfred Ewing, Director of Naval Education, the task of setting up a code-breaking organization in ‘Room 40’. Naval modern language teachers were assigned ‘special duties’. The Army sent its coded intercepts to The Cryptographic and Wireless Intelligence Organisation (which had existed since 1907) in the War Office. It eventually became known as MI1(b). Both of these organisations survived the First World War to become the Government Code and Cypher School (GC&CS) and was known under that name until 1946 when it became the Government Communications Headquarters (GCHQ).

Of the three German naval codebooks whose near-simultaneous acquisition unexpectedly put Room 40 into business, the Signalbuch der Kaiserlichen Marine (SKM) was delivered by the Russians on 13 October, the Handelsverkehrbuch (HVB) reached Britain from Australia at the end of October, and the Verkehrsbuch (VB) was dredged up in the North Sea at the end of November. For the duration of the War Room 40 worked on intercepted naval traffic, while MI1(b) concentrated on diplomatic decryption work. Initially there was some reluctance to share the contents of intercepts to those who could make best use of it. Admiral Jellicoe RN failed to exploit his advantage over the German fleet at the Battle of Jutland in May 1916 because he ‘did not trust’ the intelligence from Room 40.

Intercepts of traffic between Berlin and Madrid revealed the planned 1916 Easter Uprising in Ireland and German plan to raise fuds overseas. The most famous intercept was the Zimmermann Telegram sent to the German Ambassador in Washington in January 1917. It indicated Germany’s intention to resume unrestricted submarine warfare on 1st March, and was also intended to be forwarded to neutral countries. US and British relations were rather strained at this time as a bankrupt Britain was desperate for US armaments and other support. By March the Telegram became the tipping point for the US – it became Germany v US rather than Germany v Great Britain, and the US declared war on Germany on 4 April 1917.

Simplified examples have been included (with instructions) for the reader to try their hand at decoding. As with any two organisations, there were at times conflict between the two British agencies, with ample historic comment by co-workers in their personal papers. The Notes, Bibliography and Index are most thorough.

A fascinating look at the incredible dedication to manual decoding done long before we (now) take for granted such tasks as being done by computers (and today, by artificial intelligence!).



The RUSI – Vic Library thanks the publisher for making this work available for review.

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