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Lorenz: Breaking Hitler’s Top Secret Code at Bletchley Park
The breaking of the Enigma machine is one of the most heroic stories of the Second World War and highlights the crucial work of the codebreakers of Bletchley Park, which prevented Britain’s certain defeat in 1941. But there was another German cipher machine, used by Hitler himself to convey messages to his top generals in the field. A machine more complex and secure than Enigma. A machine that could never be broken.For sixty years, no one knew about Lorenz or ‘Tunny’, or the determined group of men who finally broke the code and thus changed the course of the war. Many of them went to their deaths without anyone knowing of their achievements.Here, for the first time, senior codebreaker Captain Jerry Roberts tells the complete story of this extraordinary feat of intellect and of his struggle to get his wartime colleagues the recognition they deserve.The work carried out at Bletchley Park during the war to partially automate the process of breaking Lorenz, which had previously been done entirely by hand, was groundbreaking and is recognised as having kick-started the modern computer age.
304 pages, Paperback
First published June 1, 2017
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September 17, 2020
Many books have a section with acknowledgements and in that section you invariably find a mention of the patient editor at the relevant publishing house. Except in this book. There is the section with acknowledgements, but not a mentioning of the editor. And that is perhaps for a good reason because the book really could do with some editing.
Captain Jerry Roberts was already a rare vintage when he started on his project and he never got to see the final result. That shows in many respects.
Essentially, Roberts has a very important and interesting story to tell us, and while he does tell it, he also spends quite a number of pages on telling us, exactly how interesting and important the story is. But that is not necessary.
Lorenz was a German World War II cipher-machine that worked with teleprinters, i.e. what elderly people remember as a telex machine, and in this way different from Enigma, which was used to encipher old fashioned Morse telegraphy. It was considered a higher grade of cipher and it would have been even more difficult to break if the Germans had taken a bit more care. But they did not.
If you use a code only once then it can be virtually unbreakable, but using it just a few more times will render it open to read for the trained code breaker.
And that is what happened. The British learned how to read German traffic of even higher grade than Enigma. That of course was an even greater scoop and consequently an even greater secret, particularly after the war. Telex was the next generation of communications after Morse telegraphy and for decades after the war everybody used it. Telling the world that you had already busted one teleprinter cipher was not a good idea as long as teleprinters remained the communications method of choice for your adversaries.
So by the seventies we heard about Enigma, but not about British successes with the Lorenz cipher.
Jerry Roberts was the last remaining of the main characters in war time breaking of the Lorenz cipher. His story is fascinating.
And it leaves me wondering what other stories we have yet to hear, because they have been even more secret.
The book is adorned with superfluous forewords, dedications, introductions, acknowledgements etc. And it is marred by repeated long sections about how much the Lorenz code breakers have been put in the shadow of Enigma. All that should have been left out. What remained would have been a true page turner. And the good bit coould have been expanded considerably if somebody had put the right questions to the author.
Captain Jerry Roberts was already a rare vintage when he started on his project and he never got to see the final result. That shows in many respects.
Essentially, Roberts has a very important and interesting story to tell us, and while he does tell it, he also spends quite a number of pages on telling us, exactly how interesting and important the story is. But that is not necessary.
Lorenz was a German World War II cipher-machine that worked with teleprinters, i.e. what elderly people remember as a telex machine, and in this way different from Enigma, which was used to encipher old fashioned Morse telegraphy. It was considered a higher grade of cipher and it would have been even more difficult to break if the Germans had taken a bit more care. But they did not.
If you use a code only once then it can be virtually unbreakable, but using it just a few more times will render it open to read for the trained code breaker.
And that is what happened. The British learned how to read German traffic of even higher grade than Enigma. That of course was an even greater scoop and consequently an even greater secret, particularly after the war. Telex was the next generation of communications after Morse telegraphy and for decades after the war everybody used it. Telling the world that you had already busted one teleprinter cipher was not a good idea as long as teleprinters remained the communications method of choice for your adversaries.
So by the seventies we heard about Enigma, but not about British successes with the Lorenz cipher.
Jerry Roberts was the last remaining of the main characters in war time breaking of the Lorenz cipher. His story is fascinating.
And it leaves me wondering what other stories we have yet to hear, because they have been even more secret.
The book is adorned with superfluous forewords, dedications, introductions, acknowledgements etc. And it is marred by repeated long sections about how much the Lorenz code breakers have been put in the shadow of Enigma. All that should have been left out. What remained would have been a true page turner. And the good bit coould have been expanded considerably if somebody had put the right questions to the author.
October 24, 2024
If you skipped the before and after section, I suggest at least read the MBE controversy.
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Jerry Roberts introduces the book as an autobiography, but the main story is about the work at Testery at Bletchley Park. He was at the time of writing the only surviving key member of the Testery, and at the same time also one of the founders.
Jerry Roberts was a linguist and does not have much insight in the mathematics of breaking. He does a good job at explaining the linguist way of breaking, with many little side stories like ”I still find myself trying to ‘break’ car number plates with 9ROEM9 or 55M889.” I had no idea that handbreaking had been such a big thing. It is crazy because having a super secure system (Lorenz) is meaningless if you misuse it badly by sending things in depth. Then it does not matter how super secure the key was, because it is not long a part of the decoding.
There are many golden bits like this about Tutte: “He established early on a method of working out the five chi wheel patterns from scratch on a single message of 4,000 characters (as opposed to a depth) which then allowed the five psi wheels and two motor wheels to be worked out.” ….“I was working in the same office as Bill Tutte when he was breaking the Lorenz system in spring 1942 and saw at first hand his endless patience and persistence. For all that time, I saw him staring into the middle distance for extended periods, twiddling his pencil and making endless counts on reams of paper for nearly three months, and I used to wonder whether he was getting anything done – my goodness, he was!”
I wish there had been more about the daily life and special breaks in the Testery. Unfortunately this part of the book is dictated by a man who has told the story over and over again, and he cannot remember what he already included in dictation. The story about Tutte’s break is there three times. Unfortunately Captain Jerry Roberts died before the book was published. I guess nobody felt they understood the content well enough to edit it.
The lacking editing and the many mistakes are my biggest points of criticism. Some mistakes are small, like he states that Hitler’s ”scientists were working on their own atomic bomb”. No, they were not. Read here: wikipedia.org/wiki/German_nuclear_pro...
They were working on a reactor to harvest the energy. They had not even calculated the critical mass of a bomb - the very first step. Another example is in a place he confuses Turing and Enigma: ”Enigma is well known for breaking the naval code.”
The problem is, we have no idea how much of the rest are mistakes or the truth. Like for instance Tutte’s ”nearly three months” sitting there alone. It does not sound right: He had to write 4000 dots and crosses into a rectangle three times. Taking 3 second per dots or cross this would take 10 hours of work, plus time to analyse the result. I think Jerry Roberts is confusing the nearly three months with the total time from start to finish, which was not Tutte alone. You can read Tuttes lecture about the break here www.cryptocellar.org/tutte/tutte.pdf
There are some obvious questions that are left unanswered (and actually also unasked): Why on earth was the Lorenz declassified that late? Those who worked with Lorenz paid a price for that. They would have liked to tell there family what they did during the war years. Many parents and spouses died before the secret was declassified. And when the secret was declassified, it seems that the English keep the de-classification a secret. Apparently Jerry Roberts only discovered it when contacted by Jack Copeland.
The pictures had a little extra surprise. A picture of Jerry Roberts first time seeing a Lorenz machine. In 2010!!! 65 years after the end of WWII he sees the machine, he spend a large part of his twenties working on. That is crazy.
Some of the content is 5-star. The edition 2 star.
---
Jerry Roberts introduces the book as an autobiography, but the main story is about the work at Testery at Bletchley Park. He was at the time of writing the only surviving key member of the Testery, and at the same time also one of the founders.
Jerry Roberts was a linguist and does not have much insight in the mathematics of breaking. He does a good job at explaining the linguist way of breaking, with many little side stories like ”I still find myself trying to ‘break’ car number plates with 9ROEM9 or 55M889.” I had no idea that handbreaking had been such a big thing. It is crazy because having a super secure system (Lorenz) is meaningless if you misuse it badly by sending things in depth. Then it does not matter how super secure the key was, because it is not long a part of the decoding.
There are many golden bits like this about Tutte: “He established early on a method of working out the five chi wheel patterns from scratch on a single message of 4,000 characters (as opposed to a depth) which then allowed the five psi wheels and two motor wheels to be worked out.” ….“I was working in the same office as Bill Tutte when he was breaking the Lorenz system in spring 1942 and saw at first hand his endless patience and persistence. For all that time, I saw him staring into the middle distance for extended periods, twiddling his pencil and making endless counts on reams of paper for nearly three months, and I used to wonder whether he was getting anything done – my goodness, he was!”
I wish there had been more about the daily life and special breaks in the Testery. Unfortunately this part of the book is dictated by a man who has told the story over and over again, and he cannot remember what he already included in dictation. The story about Tutte’s break is there three times. Unfortunately Captain Jerry Roberts died before the book was published. I guess nobody felt they understood the content well enough to edit it.
The lacking editing and the many mistakes are my biggest points of criticism. Some mistakes are small, like he states that Hitler’s ”scientists were working on their own atomic bomb”. No, they were not. Read here: wikipedia.org/wiki/German_nuclear_pro...
They were working on a reactor to harvest the energy. They had not even calculated the critical mass of a bomb - the very first step. Another example is in a place he confuses Turing and Enigma: ”Enigma is well known for breaking the naval code.”
The problem is, we have no idea how much of the rest are mistakes or the truth. Like for instance Tutte’s ”nearly three months” sitting there alone. It does not sound right: He had to write 4000 dots and crosses into a rectangle three times. Taking 3 second per dots or cross this would take 10 hours of work, plus time to analyse the result. I think Jerry Roberts is confusing the nearly three months with the total time from start to finish, which was not Tutte alone. You can read Tuttes lecture about the break here www.cryptocellar.org/tutte/tutte.pdf
There are some obvious questions that are left unanswered (and actually also unasked): Why on earth was the Lorenz declassified that late? Those who worked with Lorenz paid a price for that. They would have liked to tell there family what they did during the war years. Many parents and spouses died before the secret was declassified. And when the secret was declassified, it seems that the English keep the de-classification a secret. Apparently Jerry Roberts only discovered it when contacted by Jack Copeland.
The pictures had a little extra surprise. A picture of Jerry Roberts first time seeing a Lorenz machine. In 2010!!! 65 years after the end of WWII he sees the machine, he spend a large part of his twenties working on. That is crazy.
Some of the content is 5-star. The edition 2 star.
December 14, 2025
“The letter to be enciphered was first overlaid by the five chi wheels and then overlaid by the psi wheels, but the five psi wheels were controlled by the two motor wheels and they were always changing. In effect you had three changes applied whenever you produced a letter.”
Everyone knows about the cracking of the Enigma code, for which Alan Turing rightly got the credit. It became de-classified in the 1974. The messages were low-level, tactical and administrative. They revealed much about the activities of U-boats and this allowed Britain to survive. The Enigma machine had three (later four) rotors, scrambling text. Machines and code books were obtained and used to assist de-ciphering.
The cracking of Lorenz, by Bill Tutte, who received little credit before the author publicised it, was only de-classified in 2002. Its messages were high-level and strategic:
“I can clearly recall breaking a number of messages signed by Hitler himself – ‘Adolf9Hitler9Fuehrer9’.”
De-ciphering these messages enabled the destruction of German armies at Kursk and the success of D-day, shortening the war. The Lorenz machine had twelve rotors; no example or code book was captured until the end of the war. Bill Tutte worked it all out with nothing but the enciphered messages to go on, an amazing feat. The work was carried out manually until later in the war when a part of it was automated via the Colossus programmable computers. The initial breaking always still depended on manual work.
The purpose of this book is to redress the balance, making clear the huge importance of cracking 64,000 Lorenz messages. Captain Roberts spent great effort in this process between the revelation of Lorenz and his death in 2014.
The technical explanations are fairly clear though I didn’t understand how the break was achieved. The book is also a biography and tells of his activities post-1945. Repetitive in places but of interest.
Everyone knows about the cracking of the Enigma code, for which Alan Turing rightly got the credit. It became de-classified in the 1974. The messages were low-level, tactical and administrative. They revealed much about the activities of U-boats and this allowed Britain to survive. The Enigma machine had three (later four) rotors, scrambling text. Machines and code books were obtained and used to assist de-ciphering.
The cracking of Lorenz, by Bill Tutte, who received little credit before the author publicised it, was only de-classified in 2002. Its messages were high-level and strategic:
“I can clearly recall breaking a number of messages signed by Hitler himself – ‘Adolf9Hitler9Fuehrer9’.”
De-ciphering these messages enabled the destruction of German armies at Kursk and the success of D-day, shortening the war. The Lorenz machine had twelve rotors; no example or code book was captured until the end of the war. Bill Tutte worked it all out with nothing but the enciphered messages to go on, an amazing feat. The work was carried out manually until later in the war when a part of it was automated via the Colossus programmable computers. The initial breaking always still depended on manual work.
The purpose of this book is to redress the balance, making clear the huge importance of cracking 64,000 Lorenz messages. Captain Roberts spent great effort in this process between the revelation of Lorenz and his death in 2014.
The technical explanations are fairly clear though I didn’t understand how the break was achieved. The book is also a biography and tells of his activities post-1945. Repetitive in places but of interest.
February 3, 2023
Enigma takes up so much of the limelight that the idea of breaking another, more complex code used by the German High Command to communicate should make for a fascinating page-turner. We’re talking about intercepting messages from Hitler himself so - this should be an exciting read.
Unfortunately, this book was anything but and it’s mainly down to how it was edited.
The same phrasing used over and over and over again (yes, “without ever seeing the machine” - we know.). Concepts introduced with no context followed by whole chapters devoted to them (should be the reverse surely?). Very little explanation at points, far too much at others and the book read more like an elderly relative recounting their life story over a cup of tea while you politely listen and wait for them to remember what track they were on.
Split into three sections, the pre-war and post-war sections felt rushed (think: and then…and then…and then….) while the actual Lorenz section was definitely padded with a lot of filler material.
The author’s tone was also very bitter at points and I’m conflicted about how to feel about this. On one hand, he (and Tutte, Flowers etc.) probably did deserve more than an MBE so I understand his point. On the other hand, he’s complaining bitterly about receiving an MBE.
What I will say though is that, despite all of the glaring flaws in the book, I am glad Captain Roberts got to finally tell his story before passing away. I think the fact that more and more people will now know that Lorenz ever existed and about Tutte and Flowers is a commendable achievement even if the book is a total slog to get through.
Unfortunately, this book was anything but and it’s mainly down to how it was edited.
The same phrasing used over and over and over again (yes, “without ever seeing the machine” - we know.). Concepts introduced with no context followed by whole chapters devoted to them (should be the reverse surely?). Very little explanation at points, far too much at others and the book read more like an elderly relative recounting their life story over a cup of tea while you politely listen and wait for them to remember what track they were on.
Split into three sections, the pre-war and post-war sections felt rushed (think: and then…and then…and then….) while the actual Lorenz section was definitely padded with a lot of filler material.
The author’s tone was also very bitter at points and I’m conflicted about how to feel about this. On one hand, he (and Tutte, Flowers etc.) probably did deserve more than an MBE so I understand his point. On the other hand, he’s complaining bitterly about receiving an MBE.
What I will say though is that, despite all of the glaring flaws in the book, I am glad Captain Roberts got to finally tell his story before passing away. I think the fact that more and more people will now know that Lorenz ever existed and about Tutte and Flowers is a commendable achievement even if the book is a total slog to get through.
This entire review has been hidden because of spoilers.
May 27, 2023
Lorenz was a more complicated version of the Enigma encryption device (12 rotors compared to 3 in Enigma). The British breaking of Lorenz in World War II was not declassified until 2002, so it is not nearly as well known as Enigma. Lorenz carried messages from the German high command, while Enigma carried more tactical messages. Roberts was one of the cryptographers who worked on breaking Lorenz (carrying out the method invented by William Tutte). Roberts was one of the very few veterans of that effort alive when it was declassified, so this is a rare source (Churchill ordered the destruction of all paper records about it).
An important book, as there are so few other sources about breaking Lorenz. It's really a memoir, with a long section in the middle on his years at Bletchley Park, and how they decrypted Lorenz intercepts. He gives some technical information, but doesn't provide the background needed to make sense of it.
Unfortunately, this was written when he was old (the preface is dated 2 months before he died at 93), and some paragraphs repeat earlier information.
Overall, an easy read with a lot of information not available anywhere else, but not terribly well presented. Definitely worth reading, but certainly not perfect.
An important book, as there are so few other sources about breaking Lorenz. It's really a memoir, with a long section in the middle on his years at Bletchley Park, and how they decrypted Lorenz intercepts. He gives some technical information, but doesn't provide the background needed to make sense of it.
Unfortunately, this was written when he was old (the preface is dated 2 months before he died at 93), and some paragraphs repeat earlier information.
Overall, an easy read with a lot of information not available anywhere else, but not terribly well presented. Definitely worth reading, but certainly not perfect.
October 1, 2021
Difficult to rate this one, I gave it four stars because it's so fascinating, and lots of new stuff, I had enigma and Lorenz well mixed up before, now I know. I can't begin to imagine how they solved these codes, even after reading this, as Jerry Roberts say's it should have been impossible, even so they did it.
Basically you could read the first half of this book, and skip the second half, it's either repetition or rambling, I just skimmed through it. It's a book well worth reading for the interesting parts.
Basically you could read the first half of this book, and skip the second half, it's either repetition or rambling, I just skimmed through it. It's a book well worth reading for the interesting parts.
September 30, 2022
Whilst the actual writings a bit personalised at times the topic is absolutely fascinating about the another field of the Bletchley Park activities during the second world war. It covers an aspect that even though I knew of Enigma and Alan Turing this side was much more secretive and still covered by the official secrets act until early 2000's. An interesting read the topic of which as expressed by the author needs more recognition to assist people understanding of the part they played in the second world war behind the scenes.
May 28, 2022
Very interesting and a real live sequel to The Rose Code, which I loved. All facts as remembered by a true code breaker. A little technical in places, but definitely highlighted how difficult code breaking during WWII must have been.
June 16, 2017
Interesting reading but could have done with a good edit.
November 25, 2025
Desperately needed editing, but the core message is good and solid: after Enigma came Lorenz, and cracking Lorenz won the war much as Turing cracking Enigma won the battle of the Atlantic in 1941.
October 5, 2022
Exceptional Read
An excellent read on an unknown secret of the British G.C/C.S during World War II . And those who contributed to the war effort behind closed doors
An excellent read on an unknown secret of the British G.C/C.S during World War II . And those who contributed to the war effort behind closed doors
Displaying 1 - 11 of 11 reviews