Recently declassified documents reveal the true mission of the raid on the beaches of Dieppe on August 19, 1942.
The publicly stated reasons varied: to test Hitler’s defences in France; to placate Stalin in his calls for a second front to divert Germany’s attention away from Russia; to learn lessons in preparation for D-day (Canada’s History Magazine, Aug/Sept, 2017.)
However, the real reason was to steal the Enigma machine and give decoders like Alan Turing a chance to figure out what the Nazis were planning. It would reveal vital information about German positions, capabilities, and intentions.
Previous raids on the Norwegian island of Lofoten had been successful in stealing the three-rotor version.
Other than top command, no one knew the true mission –not the general public and certainly not the Germans. To mask the true mission, it had to look like a regular operation. Enough damage had to be done to installations to make it look convincing but not so much damage as to destroy the machines. Press reports described the large scale destruction of facilities. Not only did the propaganda bolster public moral but it deflected German attention away from the theft of cryptography. It worked at first.
But after a dozen more trawlers were taken, the Germans became suspicious and came up with a more complicated encoder: the four-rotor version of the Enigma machine. The three-rotor version was hard enough to crack but four-rotors would have been impossible without capturing more deciphering data.
Emboldened by the success of earlier raids and driven by the necessity of decoding German plans, raids became more daring and unrestrained. The ambitious “Dickie” Mountbatten was placed in charge. Three raids were planned in 1942. The first was on a U-boat base at Saint-Nazaire. It had limited success but failed to capture the ciphers and cost an entire commando unit. The second raid on the port of Bayonne was a complete failure.
Undeterred, Mountbatten pressed with the third raid on Dieppe. His leadership was in question and he had to prove himself. Not only Mountbatten’s reputation was at stake, but so was Prime Minister Churchill’s.
Canadian soldiers were languishing in England and were itching to get involved in combat. When the opportunity came in the Dieppe raid, they jumped at it.
The Dieppe plan was complicated and everything had to go like clockwork to succeed. To avoid alerting the Germans by the sound of droning planes, no bombers were used. The 14th Canadian Army Tank Regiment (Calgary) was to take Dieppe, the South Saskatchewan Regiment and Royal Regiment Canada (Black Watch) were to take adjacent beaches. Bunkers were to be attacked but not destroyed to spare the cipher equipment.
Things went badly from the start. Calgary tanks cleared the beach but got stuck in roadblocks. Other Canadian regiments were trapped on the beaches and were sitting targets for the German guns.
Six hours later, more than 1,000 soldiers lay dead on the beaches –most of them Canadians. About 2,300 were taken prisoners. No Enigma machines were captured.
October 30, 1942, the four-rotor Enigma was discovered by chance on a sunken U-boat off Port Said, Egypt.