Codebreakers: The Secret Intelligence Unit that Changed the Course of the First World War
James Wyllie and Michael McKinley
Ebury Press  352pp  £20

I am naturally suspicious of any book that sells itself by claiming to tell the story of a secret unit ‘that changed the course of the First World War’. One wonders, however, why the stories told here – in racy, journalistic tone by Wyllie and McKinley – have not before been been brought together in a single volume.

Much that they have to say about Room 40, the secret codebreaking operation at the Admiralty led by Admiral ‘Blinker’ Hall and his eccentric team of cryptanalysts, is familiar. The coup in finding three sets of German naval code books, the failures in processing intelligence at the Battles of Dogger Bank and Jutland, the triumph of decoding the Zimmerman Telegram, are all familiar.

The work of Military Intelligence 1(b) at the War Office under Malcolm Hay is less well known. As is the codebreaking of Ferdinand Tuohy on the Western Front, or Eric Gill and Reginald Thompson in the Middle East. The War Office was far slower than the Admiralty to embrace radio communications and to see the possibility of finding out what the other side was up to. Also, the descriptions of the late start in American codebreaking under Ralph Van Deman are less well known here.

The book moves from the world of the codebreakers to the cloak and dagger activities of international spies and agents. The authors discuss German agents operating in America, trying to disrupt supplies from being sent to the Allies and the attempts to prevent this by British agents. An odd cast of characters emerges, including Franz von Papen, the German military attaché in Washington (who later inadvertently helped Hitler to power) and Captain Karl Boy-Ed, the naval attaché. They recruited a team of shady,  disreputable figures to carry out acts of sabotage. The most successful was at the Black Tom wharves in New York harbour on July 30th, 1916, when 100,000 pounds of TNT and 25,000 detonators for export to the Allies were ignited. The resulting explosion had the equivalent force of an earthquake at 5.5 on the Richter Scale and was the biggest explosion in New York before 9/11.

What is so enjoyable about much First World War spying is that it was so amateurish. Most spies were gentlemen who could move about easily and freely entertain and be entertained. There is a charming quality to their undercover adventures, which reads like a John Buchan novel, that had disappeared by the era of the more ideologically-driven spying of the 1930s and the Second World War. Codebreakers is at its best when it stays within the realms of the eccentrics gathered at the Admiralty and elsewhere. It is a great story, whose legacy would lead to Bletchley Park and ultimately to the development of the modern surveillance state.

Taylor Downing is author of Secret Warriors: Key Scientists, Code-Breakers and Propagandists of the Great War (Little, Brown, 2014).

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