The Daily Telegraph - Saturday - Review
How Bletchley Park freed the Arctic
The Allied convoys were kept safe by decryption, argues David Kenyon in this engrossing history
336pp, Yale, T £16.99 (0844 871 1514), RRP £20
“So that’s what happened!” blurted out Karl Dönitz, ex-Nazi admiral, in 1974, when he learnt that British intelligence had succeeded in breaking the Enigma code during the Second World War. Only then had documents been declassified, revealing the work of Signals Intelligence (Sigint) for the Allied command. “Well,” said Dönitz, by then in his early 80s, “now you historians will have to start right back at the beginning.”
These days, it’s no secret how vital the work done at Bletchley Park was to turning back the Nazi advance. The messages that they deciphered, designated “ultra” (for ultra-secret), are still being pored over for the insight they provide into the tactical and strategic decisions made by both sides. In Arctic Convoys, historian David Kenyon uses new findings from Bletchley to retell the story of the naval battles that took place in the Arctic Ocean between 1941 and 1945 – a small but critical element of the larger Battle of the Atlantic.
The Arctic Ocean was crucial to the Allies: it was the only plausible route by which supplies could be provided to the Soviet Union, carried through freezing waters to the ports of Arkhangelsk and Murmansk. Murmansk was the easier option, as Arkhangelsk was sealed off with pack ice for much of the year. Still, reaching it was no easy feat. “With Norway occupied by the Germans,” Kenyon writes, “and the Finnish border only about 50km away to the west (Finland was at war with the USSR alongside Germany), this harbour lay dangerously close to enemy forces.”
This left the Allied ships, poorly armed cargo vessels, vulnerable to Hitler’s Kriegsmarine and Dönitz’s U-boats, which silently patrolled the seas, only gathering to strike according to “wolf-pack” tactics. The worst-hit of the convoys, PQ 17, lost 24 of its 35 ships in July of 1942 after a command to “scatter” left them vulnerable to attacks by U-boats and the Luftwaffe. This order, which came in response to the imagined threat of an attack by surface vessels, highlighted the need for a reliable way to intercept Nazi wireless communications – some 95 per cent of which were then encrypted using the Enigma cipher.
Living veterans of the Second World War are increasingly rare, but the history of Bletchley remains tantalisingly near at hand. This year we celebrated the centenary of Betty Webb, an administrator at
Bletchley, and said goodbye to Margaret Betts, one of the many Wrens responsible for the operation of the Colossus and Bombe decoding machines.
A surfeit of code names, acronyms and maritime jargon means that it isn’t easy to tell a story about naval intelligence that preserves the detail yet works for the general reader. Yet Kenyon’s authoritative prose manages to cut through, moving naturally between the military action at sea and the intelligence intrigue at Bletchley. It’s helped along by his access to a vast amount of unpublished material concerning both the convoys and the code-breaking at home; this is an unprecedentedly rich account.
The predominant narrative suggests that U-boats were the greatest threat to the Arctic convoys, but Kenyon argues that the Allies’ primary use of Sigint was to coordinate their response to the Nazi surface fleet. The turning point came at the Battle of the Barents Sea on December 31 1942, which he calls a “stunning defensive victory against superior forces”. Hitler was furious, ranting “that the surface navy was entirely useless” and
“should be scrapped en masse”. The defeat marked the end of the first Operation Regenbogen, the German code name for their surface sortie into the Arctic Ocean, and led to the increasing deployment of U-boats there. This, even so, came too late: by then, thanks to new Allied countermeasures, the U-boat was at its “least effective”.
The third part of the book is triumphant, with the Allies getting the upper hand after years of misery. Just under a year later, the Royal Navy sank the Scharnhorst, the lead ship of her class, in the final battle between British and German capital ships. Bletchley decoded their final transmission, addressed to the Führer himself, soon after it was transmitted: “We shall fight to the last shell.”
When the Nazi fleet lost the Battle of the Barents Sea, Hitler ranted furiously