Posted: January 12, 2011 in World War 2
Tags: , , , , , , , , ,

In the case of the Enigma, the first solutions were made by hand by mathematicians relying on German operators’ errors.

Harry Hinsley, assistant at Bletchley Park

The Allies’ ability to break German & Japanese codes during World War II was of critical importance – so much so that operations & lives were sacrificed rather than alert the enemy to the fact that their codes had been broken. Thousands of people worked on code-breaking, most notably at Bletchley Park in Buckinghamshire, England.

At the end of World War I the Germans had developed a cipher machine called Enigma that they thought could produce an unbreakable code. However, in the 1930s, Polish cryptologists cracked the code &, in 1939, passed their expertise onto the British who set up a top-secret code-breaking group under the gifted mathematician Alan Turing at the country house of Bletchley Park, 50 miles north of London. At the height of the war, thousands of radio intercepts a day were passing through Bletchley Park, including messages from Hitler himself. The resulting intelligence, known as Ultra, was circulated to only a restricted circle of Allied commanders. Later in the war, other German codes had to be broken. To do that the first programmable computer, called Colossus, was developed at Bletchley Park. The British won the Battle of Britain & the Battle of the Atlantic largely because they managed to read Luftwaffe & U-boat signals. Reading Hitler’s messages to his commanders also led to the destruction of German forces during Operation Overlord following the D-Day landings. Code-breaking also allowed the British to arrest German spies as well as send false intelligence & judge its effect.


We read all the Enigma signals of the German Abwehr [Military Intelligence] which meant that we captured every spy that arrived in the United Kingdom by having advanced knowledge of his arrival. Which meant that we could turn such as we needed & use them to send messages we wanted the Abwehr to receive, & monitor the reception & the reaction of the Abwehr. All that signal intelligence underlay the effective use of what was called the Doublecross Operation for the purposes both of stopping German reception of intelligence – other than false intelligence – & also of creating deception by sending them false intelligence.


The Germans supplied Enigma machines to the Japanese, who developed their own code called Purple. The British broke this too & handed over the “Magic” decoders to the US in time for American code-breakers to decipher the diplomatic traffic between the Japanese Embassy in Washington & Tokyo before Pearl Harbor (December 7th, 1941). Although this failed to alert the US to the attack, decrypting Japanese messages played a significant part in US naval victories in the Coral Sea & at Midway in 1941-42. It also allowed American pilots to shoot down the plane carrying Admiral Isoroku Yamamoto, the architect of the Pearl Harbor attack, on April 18th, 1943.

  1. […] This post was mentioned on Twitter by Vera Mae, Vera Mae. Vera Mae said: Code-Breaking: […]

  2. vimax says:

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  3. Armando says:

    Highly descriptive post, I loved that bit. Will there be a part 2?

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