Crackers – Military History’s Most Famous Code-Breakers

The code breakers at Britain's Bletchley Park helped the Allies track down and destroy the German U-boats.

Thanks to the efforts of code breakers at Britain’s Bletchley Park, Allied planes and warships were better able to track down and destroy German U-boats.

“While The Imitation Game will certainly put British wartime cryptanalysis back into the spotlight, the annals of military history are filled with other intriguing stories of codes and the people who broke them.”

Alan Turing.

THE AMAZING STORY BEHIND BRITAIN’S effort to crack the Nazi Enigma code is set to hit the big screen in North America later this week. The Imitation Game, which stars Benedict Cumberbatch and Keira Knightley, follows the rise and fall of celebrated Bletchley Park cryptanalyst Alan Turing. The mathematician turned wartime code-breaker was one of the brains behind “the bombe”, a revolutionary early computer that British intelligence used to crunch Hitler’s famous World War Two military code. Yet despite his monumental contribution to the Allied victory, Turing was prosecuted in 1952 for “gross indecency” following the discovery that he’d been having a romantic affair with a male colleague. Following the conviction, the 39-year-old “father of computer science” was ordered to undergo a battery of harsh chemical treatments designed to cure him of his homosexuality. The process rendered him physically and emotionally shattered. Two years later he poisoned himself with cyanide. In 2009, the British government formally apologized for what it characterized as its “appalling” persecution of Alan Turing. While The Imitation Game will certainly put British wartime cryptanalysis back into the spotlight, the annals of military history are filled with other intriguing stories of codes and the people who broke them. Here are some of the more famous ones.

The German military’s answer to Bletchley Park was codenamed B-Dienst. (Image source: WikiCommons)


Unlike the British, who concentrated the bulk of their code breaking efforts under one roof, Nazi Germany left the task to a disjointed hodge-podge of secret departments, offices and bureaus almost as cryptic as the ciphers they worked to demystify. For example, Hermann Goering’s pre-war Forschungsamt or Air Ministry research office maintained a special section for listening in on and descrambling Allied communications, as did the Luftwaffe itself. The Wehrmacht had a myriad of code-breaking divisions too. Separate groups in the OKW focused on the Eastern Front as well as the war in the west. Above both of those operations was a cryptanalysis section reporting to the army high command itself. Then there was a code cracking outfit within the army counter intelligence division. Naval headquarters maintained a decryption section too. Even the Nazi postal service, Deutsche Reichspost had a cryptanalysis wing! Perhaps the most effective of all the Nazi organs was the top secret B-Dienst. Established prior to the war, the secretive unit had unravelled Royal Navy and merchant fleet codes as early as 1935, and by 1941 was even reading U.S. Navy signals – all of which provided invaluable intelligence to U-boat wolf packs in the Atlantic. In fact, as late as 1943, B-Dienst was deciphering up to 80 percent of Allied naval codes, however only a fraction of the intercepts were being cracked in time to prove useful. [1] Had the Nazis concentrated all of their cryptanalysis efforts into one central bureau, it’s likely the war might have unfolded much differently.

American code breakers deciphered Japanese a tough naval code prior to the Battle of Midway. When the Japanese fleet arrived to capture the vital island outpost, U.S. Navy ships and aircraft were waiting for them.

American intelligence deciphered Japan’s JN-25 naval code prior to the Battle of Midway. When the Japanese fleet arrived to capture the vital island outpost, U.S. Navy ships and aircraft were already waiting for them.


As early as the 1920s, U.S. military cryptographers were intercepting and decoding Japanese naval and diplomatic cables. The joint army and navy outfit tasked with the eavesdropping was known as Magic. And as the Japanese strengthened their ciphers throughout the 1930s, the top-secret Washington-based cryptanalysis team continued to decode them. In fact, it was said that Magic could decipher Japanese codes faster than the intended recipients could. Following the 1940 pact between Berlin and Tokyo, Germany passed its Enigma technology to its new ally in the Pacific to help them further scramble communications. U.S. intelligence designated this new code “Purple”. It too was broken by Magic technicians. While the group failed to detect any specific threat related to the Japanese attack on Pearl Harbor, it did descramble an ominous 14-part communiqué to the Japanese embassy in Washington on the morning of Dec. 7, 1941 instructing the ambassador to formally sever diplomatic ties with the U.S. in advanced of an unspecified event. Fortunately, America’s military code breaking sections would prove more useful months later when messages sent using Japan’s new naval cipher JN-25 were  decrypted by the navy’s OP-20-G office. The breakthrough provided advanced warning that IJN carriers were massing for a strike on the U.S. base at Midway in June of 1942. Unlike the fiasco at Pearl, on this occasion, America’s navy was better prepared and dealt Japan a crippling blow in the ensuing three-day naval battle.

Poland was the first country to lay its hands on Enigma technology. It transferred its knowledge of the famous code machines to the Allies in 1939.

Poland was the first foreign power to lay its hands on German Enigma-like technology. It transferred knowledge of the famous code machines to the Allies in 1939.

The Cipher Bureau

While Germany’s Enigma cipher was famously divined by the tireless work of cryptanalysts at Bletchley Park, it was actually Polish code-breakers with that country’s Biuro Szyfrów or Cipher Bureau who laid much of the groundwork for Britain’s later successes. As early as 1932, intelligence experts in Warsaw were demystifying early iterations of the notorious Nazi code. Amazingly, in 1928 a prototype of a commercial German code machine, similar to an Enigma terminal, fell into the hands of keen-eyed Polish customs officials. Intelligence experts in Warsaw seized the machine and painstakingly disassembled it for study before handing it back to its rightful German owners. The coup provided Poland with valuable insight into future Nazi cryptography. For the next decade, the Cipher Bureau descrambled Third Reich communiqués with growing success. In fact by the summer of 1939, Polish intelligence was largely aware of Hitler’s intention to invade. Weeks before the German attack, Warsaw transferred the sum of its knowledge of Enigma to the British government, providing the newly established Bletchley Park with a virtual treasure trove of knowledge upon which to build. In many ways, Poland’s Biuro Szyfrów helped the Allies win the Second World War before the conflict’s first shots had even been fired.

Codebreaking was in its infancy during World War One. The first ‘experts’ in the field were mostly self-taught amateurs.

Room 40

A generation before Bletchley Park, there was was Room 40 – Great Britain’s little-known World War One cryptanalysis section. Located in London’s Whitehall, the largely amateur outfit was secretly formed in October of 1914 to make sense of a cache of encrypted documents and a code book recovered from a German warship that had recently foundered in the Baltic. Later, the dozen or so volunteer linguists, engineers and cryptography enthusiasts attached to Room 40, along with intelligence officers at MI1, would pore over intercepted signals to work up a basic understanding of Germany’s rudimentary ciphers. Eventually, the unit hit pay dirt when it cracked a 1917 German diplomatic cable to Mexico. It was a development that ultimately changed the course of the war. Known as the Zimmerman Telegram after the Kaiser’s foreign secretary, the document from Berlin pledged military support to the Mexican government if the latter sought to recapture lost territory in the southwestern United States. Britain eagerly forwarded the contents of the secret proposal to Washington. Not springily, the details inflamed the American public. In fact, the revelation, along with Germany’s recent resumption of unrestricted submarine warfare in the Atlantic, is seen as one of the major factors behind the United States’ entry into the war in Europe.

1 comment for “Crackers – Military History’s Most Famous Code-Breakers

  1. Alex E
    25 November, 2014 at 11:44 am

    An interesting postscript to the Enigma story is that it was the gift that kept on giving. After 1945, the Soviets captured large numbers of German Enigma machines and (as the UK hadn’t told them otherwise) believed they were still un-breakable. The USSR used them widely in their military and intelligence agencies and also supplied them to their communist allies around the world. The West could read all this traffic for years and years – until a Soviet mole blew the whistle. Shortly afterwards, the Enigma story was declassified and made public.

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