Image attribution: Bundesarchiv, Bild 101II-MN-1361-16A / Winkelmann / CC-BY-SA 3.0

On May 24th 1941, the German battleship, Bismarck, sank HMS Hood, the largest warship in the Royal Navy in the Denmark Straits between Iceland and Greenland. Unknown to the British at the time, Bismarck was short on fuel, and her Commander, Admiral Lutjens, had signalled, using German naval enigma encryption that it was his intent to run to Brest in western France. The Government Code and Cyber School at Bletchley Park, (BP), could not read this particular code2 and no useful intelligence was obtained.

A second piece of signal traffic relating to Bismarck was also intercepted at Bletchley Park. This message had originated in occupied Athens if Greece, where the Chief of Staff of the Luftwaffe, General Hans Jeschonnek, signalled Berlin asking for information on Bismarck as he had a relative aboard. The reply message back to Jeschonnek stated her course was to Brest, used the Luftwaffe enigma code, which BP could decrypt using a Bombe machine. The following morning, the decrypted message was passed to Jane Fawcett, her job was translate the German into English, Fawcett read the original German and saw that the Bismarck was approximately 700 miles from Brest, and not Norway as was the British assessment prior to the decryption of the message.3 Royal Air Force ordered its brand new long-range Catalina seaplanes out into the Atlantic to find Bismarck. Each plane was given a grid square of approximately 100 square miles to search; a U.S. Navy pilot named Leonard Smith, posted to help training British aircrews in direct breach of then US neutrality, piloted one Catalina from 209 squadron. Smiths plane located Bismarck early on the 26th, reported its course and speed, which was sufficient to allow the Royal Navy to intercept and sink Bismarck on the 27th.

By Paul Teare