Australian code breakers in World War II

Many thanks to SWLing Post contributor, Ian P, for sharing the following from the radio program, ABC Overnights:

The crucial role of Australian code breakers in World War 2

Thanks to the recent film, The Imitation Game, you may be familiar with the story of how British intelligence, led by mathematician Alan Turing, cracked Nazi codes during WW2. Did you know there were also two secret organisations in Australia working to break Japan’s military codes?

These were staffed with brilliant cryptographers, including some who had studied mathematics and the classics, and others who had lived or grown up in Japan. By patiently and carefully unravelling the codes in Japanese signals, their intelligence played a crucial role in the battles of Midway and the Coral Sea, as well as the push into the Philippines.

Trevor Chappell interviews Craig Collie, author of the book Code Breakers – Inside the Shadow world of Signals Intelligence in Australia’s two Bletchley Parks.

Duration: 36min 36sec
Broadcast: Mon 10 Apr 2017, 1:00am
Published: Mon 10 Apr 2017, 4:43pm

Listen to the full program/interview via the embedded player below:

Click here to download the MP3 or click here to listen on the ABC website.

I’ve also noted that you can pre-order Code Breakers – Inside the Shadow world of Signals Intelligence in Australia’s two Bletchley Parks at There is no expected delivery time yet, however.

Code Breakers is available directly from the publisher in Australia–click here to view.

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14 thoughts on “Australian code breakers in World War II

  1. Daryl Beattie

    I see a lot of comments here about the conspiracy theories that abound. The simple explanation, that things are exactly what they are is evident from the simple logic test that no conspiracy theory likes. All were predicated on the idea that FDR needed Japan to attack the USA to get us into WWII so he withheld vital information allowing us to have the disaster at Pearl. (Some people add in that it was Churchill doing it, or who ever they want to target). This is all traced back to a disgruntled isolationist/Anti FDR fanatic who created the concept soon after the attack, and has been elaborated on since.

    If FDR needed an excuse to get into the war, the overlooked logic is that he certainly did not need a DISASTER to start it. Frankly, just the fact the Japanese were in the act of attacking the US Fleet while we were working things out with their Peace commissioners in Washington would have been good enough to arouse the nation. Thus, if we had SANK the Japanese Fleet, (and shown that the US Navy and Army Air Force was competent), he would still have his war, and have retained something to fight it with, without all that messy egg on his face.

    The same goes for the British or Australians. WE ALL KNEW THEY WERE THE TARGET. It makes no sense for them to allow us to be hurt in such a way that we could not come to their aid. Thus all the historical facts of behind the scenes Allied work to avoid an American war with Japan makes sense. FDR and Churchill knew they were doing good to keep it one enemy at a time with them holding off the Nazis and us being able to gear up to supply the tools of war. They simply were not stupid.

  2. Pingback: The RAAF No. 4 Wireless Unit: Never to march, never to be mentioned | The SWLing Post

  3. Ross

    I’m not sure of the correctness of this however I have heard a number of claims by Australian signal men that Japanese radio traffic was intercepted if I remember correctly in Western Australia regarding an imminet attack on Pearl Harbour or on American Pacific assets.
    Supposedly this was priority passed to Australian high command and on to the British who at a very top level either deliberately dithered or withheld the info for the reasonage of bring the Americans into the war due th their hitherto isolationist position.
    Churchill was struggling to obtain US support at this time.
    Obviously this would be kept very quiet and denied afterwoods by the British.
    Has any one else heard of this.

    1. DanH

      I have read a number of variations of this hypothesis, including FDR (not Churchill) withholding the vital warning. Perhaps the best tool is understanding what Japanese codes were broken by December 1941. The Purple code or diplomatic code was broken by this time but these messages would not have included military information which was kept secret from the Japanese diplomatic services. JN25, the family of Japanese naval codes was put into use in in 1939 and was updated every 3-6 months. Each update required fresh code cracking. Prior to December 1941 only 10% of JN25 was known. JN25b was used beginning on December 4, 1941. This code was broken sufficiently by May of 1942 to provide warning of the attack on Midway. The Japanese carrier task force left Japan for Pearl Harbor on November 26 and maintained strict radio silence.

  4. Neil Bolitho

    Never to March, never to be mentioned.
    Since the end of the Second World War, many thousands of returned service personnel have marched at Anzac Day services throughout Australia.
    My father never marched.

    My father served in RAAF No 4 Wireless Unit, Central Bureau.
    Central Bureau was under the direct command of General Douglas MacArthur, and was set up to detect, record, and translate all messages transmitted by Japanese forces in the Pacific.

    Central Bureau was headquartered in Brisbane, but its Wireless Units worked in the field, moving forward with MacArthur, constantly intercepting and decyphering enemy messages.
    As the war progressed, the units became so efficient in their work that they were monitoring all enemy radio traffic, and in fact frequently knew the Japanese intentions before the messages reached their intended destination.
    The Wireless Units served throughout the Pacific islands providing vital information about enemy strengths and positions.
    RAAF No 4 Wireless Unit was formed as a highly mobile unit, and served at Hollandia, Morotai, Labuan Island, and at Luzon, Philippines.
    The U.S. High Command highly praised the Wireless Units of Central Bureau, stating that their work effectively shortened the War in the Pacific by at least two years.

    At the end of the war, Central Bureau was dismantled. All personnel signed a lifetime secrecy order to not speak of their wartime activities.
    No promotions applied. No evidence of their Central Bureau service was recorded, including overseas service. No medals were struck.
    Family members, including children, were not told in any detail, of their father’s war experience.

    It was only in the late 1990’s that the Australian government allowed information to be released.
    In the early 1960’s, my father mysteriously went on an unexplained visit to Brisbane.
    It was not until over thirty years later that I found out that he attended a twenty-year anniversary of his unit’s graduation.
    I write this on behalf of the children and grandchildren of those Central Bureau personnel that served diligently and efficiently when called upon, and who, when the job was done, quietly went home. They are our heroes.

    – Neil Bolitho

  5. Rob Wagner

    Code Breakers is also available NOW on Kindle if you go to the Australian Amazon store (….yes, we have an Amazon online outlet now, too!). The link is:
    I don’t know if this link will work for those customers outside Australia (there may be territorial restrictions placed on this), but perhaps worth a try.
    You’ll notice that there are a number of books available using the title “Code Breakers” (or similar), so be sure you’re selecting the one by Craig Collie. Happy reading!

  6. DanH

    Mr. Chappell provides some interesting and previously unknown insights into the widely dispersed Allied signals intelligence network active in the Pacific during WWII. Here are a few additional facts regarding the shoot-down of Admiral Yamamoto. The original message, NTF131755, addressed to the commanders of Base Unit No. 1, the 11th Air Flotilla, and the 26th Air Flotilla, was encoded in the Japanese Naval Cipher JN-25D (Naval Operations Code Book of the third version of RO), and was picked up by three stations of the “Magic” apparatus, including Fleet Radio Unit Pacific Fleet. Operation “Vengeance” was the flight of twelve P-38 Lightning twin engine fighters sent to shoot down the “Betty” bomber that carried Admiral Yamamoto. Four P-38s found Yamamoto’s plane. Chappell mistakenly refers to these aircraft as “bombers”. As an aside, my Dad served as a fleet radioman in the Pacific during the first three years of the war. He said it it was very easy to find some Japanese code transmissions while at sea because unlike the Allied signals the Japanese transmissions were MCW. I suspect MCW was used for relatively local traffic.

    1. Michael Black

      That’s interesting assuming “MCW” is “modulated CW.

      So it’s a regular AM transmitter, with an audio oscillator that can be keyed that feeds the microphone jack.

      There’s no technical advantage, but it’s not efficient. You don’t need a BFO at the receiver, but over distance, CW would carry further. So it doesn’t make sense. Cheap license free walkie talkies often had a button for sending MCW, and hams have used it to send morse code practice sessions on VHF, where the average ham would only have an AM or later FM receiver.


      1. DanH

        Yes. MCW is modulated continuous wave. The usage of MCW for sending code actually predates widespread use of CW.

        1. rtc


          IIRC both the Gibson Girl portable 500 kc transmitter
          (all you did was turn a crank) and shipboard radio
          shacks used mcw.
          Did your dad ever mention copying 500 kc stuff?

          1. DanH

            No, not specifically. But I assume he monitored all frequencies and modes except radar as he served mostly on destroyers. In addition to screening the aircraft carrier(s) destroyers were frequently sent after downed pilots. The only frequency specialists on board were what my Dad called the “radar boys” who did not handle communications. Dad served on the Gridley DD-380 which had full fleet communications and cipher capability. It was equipped to provide full back-up communications for the flagship: USS Enterprise, if needed.

  7. JAYoung

    Interesting converation about the Japanese code-breaking from an Australian perspective.
    In the end it was the arrogance of the political and military leadership of both Japan and Germany that led to their codes being broken. Their superiority complex refused to admit the evidence — like the Yamamoto shoot-down — and kept them from acting on what certainly some of their own experts told them.
    The Allied democracies, in contrast, were much more open to dissenting opinions.
    It’s a lesson we may have to learn again in today’s world.

  8. John Howieson

    Here’s a dose of reality. In the case of the Germans vs the rest of us, a new scrambled code became more & more frequent. This code break became one of the greatest “Win or Lose” factors at this point in WWII!


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