The German radio station WDR5 has aired a report about Enigma spy Hans-Thilo Schmidt. Among the experts quoted are Dermot Turing and me.

Hans-Thilo Schmidt (1888-1943) was a spy who, during the 1930s, sold secrets about the German Enigma encryption machine to the French. The material he provided facilitated the reconstruction of the Enigma rotor wirings by Polish mathematicians. As a consequence, the Poles were able to read a large proportion of Enigma-enciphered traffic for a couple of years.


The Enigma spy

A former officer, Schmidt had been forced to leave the army having suffered from gas during the First World War. However, his brother, Rudolf Schmidt, secured him a post at the German army’s cryptographic unit. After the military version of the Enigma was introduced, Schmidt contacted a French intelligence officer and offered to supply information about this machine. His offer was accepted.

For the next several years, Schmidt met with French intelligence agents regularly and provided them an Enigma manual, operating instructions, and key lists. Even with this information, however, French cryptologists were unable to decipher Enigma messages. British cryptologists, who were informed by their French colleagues, couldn’t break the Enigma either.

In 1932, the French shared intelligence obtained from Schmidt with the Polish crypto unit. Mathematician Marian Rejewski had already set up a system of equations describing the operation of the German Enigma rotor-wirings. The keys provided by Schmidt helped fill in enough of the unknowns in Rejewski’s formulae, allowing him to solve the equations and recover the wirings. Henceforce, the Poles were able to read Enigma traffic for nearly seven years.

Based on the work of Rejewski and his fellow mathematicians, the British were able to construct a powerful Enigma deciphering machine, the Turing-Welchman Bombe, which enabled them to break a large proportion of the German Enigma traffic during World War II.

In 1943, Schmidt’s case officer, was arrested by the German police. He betrayed Schmidt as a French spy. Schmidt was arrested and died in prison a few months later – probably because of suicide.

It is justified to say that Hans-Thilo Schmidt’s spying, which started years before the Second World War, had a major impact on the course of the war. It is even possible that without Schmidt’s work the Enigma would not have been broken at all.


The Zeitzeichen radio report

A few weeks ago, journalist Martin Herzog from the German radio station WDR5 contacted me. He was working on a report about Hans-Thilo Schmidt. This report was to be aired in the WDR5 Zeitzeichen series, a daily radio feature that covers historic events that have taken place on the same day of the year. In this case, the historic event was Hans-Thilo Schmidt’s death on September 19th, 1943. Jochen Viehoff, director of the Heinz Nixdorf Museum, had recommended me as an interview partner.

The interview with Mr. Herzog …


… took place in the office rooms of my employer cryptovision. Our talk about Schmidt, the Enigma and a few related topics lasted about half an hour.

When Mr. Herzog asked me if I knew other interesting people he could interview about Hans-Thilo Schmidt, I recommended Sir Dermot Turing, …


… the nephew of Enigma codebreaker Alan Turing.

On September 19th, 1943, the 75th anniversary of Schmidt’s death, Martin Herzog’s radio report about Hans Thilo Schmidt was aired. It contains statements by Dermot, Mr. Viehoff and me. To my regret, there is no English version. Click here to listen to it.

Further reading: Enigma sells at $547,500


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Kommentare (5)

  1. #1 Klaus Schmeh
    21. September 2018

    Gert Brantner via FaceBook:
    …”A machine called the “bombe” is used to expedite the solution. The first machine was built by the Poles and was a hand operated multiple enigma machine. When a possible solution was reached a part would fall off the machine onto the floor with a loud noise. Hence the name “bombe”.

    A different version goes that Rejewski named his baby after a certain ice cream creation sold in vicinity of his office.”

  2. #2 Klaus Schmeh
    21. September 2018

    Bart Wenmeckers via FaceBook:
    I knew of the Schmidt details prior to this article but I also wonder what the out come would have been if the information had not been disclosed. The poles were passed a mass of valuable intelligence and years to research. the poles were capable of reading german enigma messages however the germans added an extra rotor just before the invasion of poland which the cryptanalysist didn’t resolve in time.

    This Spy case and its crypto breah implications remind me of the John Walker spy ring during the coldwar era.

    Good article as always Klaus
    Thanks for sharing.

  3. #3 The Piper
    23. September 2018

    Umm.. as far as i know these informations were not shared with Marian Rejewski, because his supervisor decided, they should break the enigma on their own, since they were already quite successful. This way they would gain more informations about enigma instead of just using the shared informations from Schmidt.

    They used an official bought version of a non military version of the enigma to understand the principe of the enigma in general.

    Wikipedia either doesn’t mention that Rejewski used informations shared by Schmidt:

    So it looks to me like the brits and french were not able to break enigma with Schmidt’s informations, but Rejewski and his comrades did it without those informations.

  4. #4 Klaus Schmeh
    23. September 2018

    Paul Kellar via email:
    Success! see :

  5. #5 Emma Canning
    8. November 2020

    That is very interesting story. For sure it changed the movement of the whole war. Otherwise, it would finish different