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The Bletchley Park Codebreakers
Bletchley Park was the site of Britain's main decryption center, the Government Code and Cypher School. This extraordinary book includes essays by some of Britain’s foremost historians and academics and traces the legacy of Bletchley Park from the innovative work which led to the breaking of Enigma and other wartime codes to the invention of modern computing and its influence on Cold War codebreaking.
Crucially, it also features contributions from former Bletchley Park codebreakers, whose personal reminiscences and very human stories of life and work in wartime Bletchley make compelling reading.
Michael Smith is the author of Killer Elite.
Ralph Erskine is one of Britain’s leading historians of wartime codebreaking.
Crucially, it also features contributions from former Bletchley Park codebreakers, whose personal reminiscences and very human stories of life and work in wartime Bletchley make compelling reading.
Michael Smith is the author of Killer Elite.
Ralph Erskine is one of Britain’s leading historians of wartime codebreaking.
560 pages, Paperback
First published January 1, 2001
31 people are currently reading
319 people want to read
About the author
Michael Smith
26 books48 followersThere is more than one Michael Smith in the database.
Michael Smith is a British author and screenwriter who specializes in spies and espionage.
Source: Wikipedia.
Michael Smith is a British author and screenwriter who specializes in spies and espionage.
Source: Wikipedia.
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Displaying 1 - 17 of 17 reviews
May 6, 2020
I visited the Bletchley Park site in July 2019 and thought I ought to buy one of the many books offered in the gift shop. The issue was, which one? TV “documentaries” on the wartime activities at Bletchley often seem to push a particular agenda. For that reason I went for this book of essays by different authors. Some of the chapters are contributed by historians whilst others are personal recollections from those who were there (the book was originally published in the nineties). Unsurprisingly most of the authors are British, although American historians David Alvarez and Stephen Budiansky have a chapter each covering UK-US cooperation on intelligence (or sometimes, the lack of it).
One thing I would say is that some of the chapters are very technical. That was especially true of those by Keith Batey and Shaun Wylie, both of whom were codebreakers. To tell the truth I gave up trying to understand Shaun Wylie’s piece. Personally I’m more interested in how the codebreaking affected the course of the war than I am in the detail of the techniques used. That said, I found the chapter by the German-born codebreaker Rolf Noskwith to be one of the best in explaining some of the process to the layman. Another codebreaker, Mavis Batey, provided a lively account of her role in breaking the Italian naval codes. She worked in a section staffed mainly by young women and headed by Dillwyn “Dilly” Knox, who had been an outstanding cryptanalyst in WW1. The breaking of the Italian codes allowed the Royal Navy to win a one-sided victory at Cape Matapan off the coast of Greece. Most of the time the codebreakers didn’t know what use was made of the information they provided, but on that occasion the Director of Naval Intelligence rang Bletchley with the message: “Tell Dilly that we have won a great victory in the Mediterranean and it is entirely due to him and his girls.” As Batey said in her account, it was all heady stuff for a 19-year-old.
Discussion about Bletchley has tended to focus on the breaking of the German Enigma encryption device, which of course the book covers. However it also offers a much more comprehensive account. Until I visited the site I didn’t even know that there were sections at Bletchley working on breaking Japanese codes, something this book describes as “an undervalued effort.” One of the most interesting sections related to Churchill’s controversial decision to switch British support for the Yugoslav resistance from the royalist Chetniks to the communist Partisans. I’d always understood this had resulted from the mission to Yugoslavia by Fitzroy Maclean, but historian John Cripps suggests that Maclean’s mission was little more than a cover, and that Churchill already knew all he needed to from decoded sigint from Yugoslavia. Churchill had to justify his decision to the House of Commons but couldn’t of course make reference to Bletchley, so for public consumption claimed that the decision had been based on Maclean’s report. It’s always interesting when a history book challenges my preconceptions.
For me this book would probably rate as a 7/10. Some of it is quite dry but those sections are outweighed by the wealth of new information I got out of it. The rating is rounded up to four stars.
One thing I would say is that some of the chapters are very technical. That was especially true of those by Keith Batey and Shaun Wylie, both of whom were codebreakers. To tell the truth I gave up trying to understand Shaun Wylie’s piece. Personally I’m more interested in how the codebreaking affected the course of the war than I am in the detail of the techniques used. That said, I found the chapter by the German-born codebreaker Rolf Noskwith to be one of the best in explaining some of the process to the layman. Another codebreaker, Mavis Batey, provided a lively account of her role in breaking the Italian naval codes. She worked in a section staffed mainly by young women and headed by Dillwyn “Dilly” Knox, who had been an outstanding cryptanalyst in WW1. The breaking of the Italian codes allowed the Royal Navy to win a one-sided victory at Cape Matapan off the coast of Greece. Most of the time the codebreakers didn’t know what use was made of the information they provided, but on that occasion the Director of Naval Intelligence rang Bletchley with the message: “Tell Dilly that we have won a great victory in the Mediterranean and it is entirely due to him and his girls.” As Batey said in her account, it was all heady stuff for a 19-year-old.
Discussion about Bletchley has tended to focus on the breaking of the German Enigma encryption device, which of course the book covers. However it also offers a much more comprehensive account. Until I visited the site I didn’t even know that there were sections at Bletchley working on breaking Japanese codes, something this book describes as “an undervalued effort.” One of the most interesting sections related to Churchill’s controversial decision to switch British support for the Yugoslav resistance from the royalist Chetniks to the communist Partisans. I’d always understood this had resulted from the mission to Yugoslavia by Fitzroy Maclean, but historian John Cripps suggests that Maclean’s mission was little more than a cover, and that Churchill already knew all he needed to from decoded sigint from Yugoslavia. Churchill had to justify his decision to the House of Commons but couldn’t of course make reference to Bletchley, so for public consumption claimed that the decision had been based on Maclean’s report. It’s always interesting when a history book challenges my preconceptions.
For me this book would probably rate as a 7/10. Some of it is quite dry but those sections are outweighed by the wealth of new information I got out of it. The rating is rounded up to four stars.
May 2, 2015
This would have to be the definitive word on what went on at BP – as opposed to the gossipy Secret Life of BP. What blows me away is the extreme level of effort and sheer ingenuity that was poured into the project (and what a totally inadequate description that is). That, and the utter tedium of working for years at some fragment, the purpose of which, because of the total secrecy, was never revealed until much, much later.
Of course at some level, I was aware that code keys changed all the time, so the work was never finished, but until I read this book I had not realized there were so many different codes to be broken (and some that never were) so often, and the continual stress that that produced.
Since it’s a collection of first-person accounts there is some overlap in the material, but far from being repetitive, I found that really useful: some explanations of the codes themselves and code-breaking techniques were quite impenetrable, but other accounts made the same information crystal-clear. (after a couple of re-readings, it’s that sort of book. ). Codebreakers actually covers the period from about 1920 almost to the present, though I wasn’t so interested in the post-war era when the focus morphed from decryption to espionage.
Many of the narrators and essayists died even before the original publication in 2001 (as Action This Day) so this is truly a unique record, as a lot of the information they shared had not been widely available much before then. I found it interesting that the first books to be published about BP often got it wrong because the authors weren’t aware then of work outside their own area. I’m thinking particularly of the development of the computer; this was the story I mistakenly thought was in Dyson's somewhat drivelly Turing's Cathedral. Such a shame that excessive secrecy prevented names like Tommy Flowers being known as the practical inventor, even now.
There are some brilliant essays here, though a few (by one of the editors, Ralph Erskine, mostly) are next to unreadable with their dense records of daily statistics, office procedure and jargon. Others just echo the tedium of what must have been 99% of the work at BP; but can you imagine what it must have been like, 30-odd years later, to be able to say, “so that’s what I was doing!”?
September 11, 2014
An interesting account of both life at Bletchley Park as well as techniques used to break some non - Enigma codes and cyphers. The emphasis here is not on famous people, such as Turing, but rather on those working "in the trenches." Also included is a history of British code breaking between the two world wars as well as during the Cold War.
May 20, 2018
This collection of more than 20 essays and personal reminiscences provides a well rounded although not fully organized description of how the WWII codebreaking operation at Bletchley Park operated. Many of the technical descriptions were impenetrable for me and likely will be to most other readers; I'm not sure why the editors could not have tried harder to have things explained on a more basic level. However, these minor annoyances are outweighed by the book's strengths.
First, it puts a number of aspects of the effort into a new light: the staffing was massive, about 10 times as large as I'd thought; the successes depended on several brilliant and largely unsung people doing astonishing work in sorting out the intricacies of both code and electro-mechanical equipment; the codebreaking achievements were spotty and were frustrated more often than I'd thought by German security measures; the codebreaking process was much more complicated than the picture usually drawn around the sight of messages simply being captured and fed into machines that were forerunners of computers; the problems were constantly shifting because of continual changes in German signalling practice, requiring adaptation as frequent at Bletchley as on battlefields.
Then there are the glimpses into personal experience. Among the most poignant is the rebellion by some of the analysts against codebreaking efforts being applied to allies at the end of the war. This surprising intrusion of morality supports an impression left by the incredibly tight security that for decades surrounded the entire operation despite thousands of people taking part in it — the war's outcome depended in large part on personal integrity shown by countless numbers of ordinary as well as extraordinary people.
(I read the early edition titled Action This Day. That title made the book sound a bit like it would involve battle description; it actually refers to a high-priority classification of directives from Winston Churchill.)
First, it puts a number of aspects of the effort into a new light: the staffing was massive, about 10 times as large as I'd thought; the successes depended on several brilliant and largely unsung people doing astonishing work in sorting out the intricacies of both code and electro-mechanical equipment; the codebreaking achievements were spotty and were frustrated more often than I'd thought by German security measures; the codebreaking process was much more complicated than the picture usually drawn around the sight of messages simply being captured and fed into machines that were forerunners of computers; the problems were constantly shifting because of continual changes in German signalling practice, requiring adaptation as frequent at Bletchley as on battlefields.
Then there are the glimpses into personal experience. Among the most poignant is the rebellion by some of the analysts against codebreaking efforts being applied to allies at the end of the war. This surprising intrusion of morality supports an impression left by the incredibly tight security that for decades surrounded the entire operation despite thousands of people taking part in it — the war's outcome depended in large part on personal integrity shown by countless numbers of ordinary as well as extraordinary people.
(I read the early edition titled Action This Day. That title made the book sound a bit like it would involve battle description; it actually refers to a high-priority classification of directives from Winston Churchill.)
April 29, 2012
This book is really a collection of essays and recollections of the history of Bletchley Park, intelligence gathering and of codebreaking. There are several writers, some of them historians, some of them former employees at Bletchley and this makes for differences in style between many of the chapters.
It took me longer than expected to read this book. Some chapters were heavy going, especially the ones that went into detail on codebreaking. I found it hard to follow the methods explained at times and as this book has only one other review here I don't know if the deficiency is with my understanding or with the book's ability to explain. I've also read Enigma by Hugh Sebag-Montefiore and managed to follow the methods explained there so I hope the fault is not all mine.
On the plus side, this book contains much more than just details on how the codes were cracked. There are many chapters on the development of intelligence gathering, intercepting signals and the politics, both national and international, involved. There is much information about the personnel too, not just the well known codebreakers, and explanations of the work of the less glamorous departments.
In summary this was full of fascinating information and was mostly well written, but if you're looking for detailed explanations on the methods of Turing et al. this is probably not that book.
It took me longer than expected to read this book. Some chapters were heavy going, especially the ones that went into detail on codebreaking. I found it hard to follow the methods explained at times and as this book has only one other review here I don't know if the deficiency is with my understanding or with the book's ability to explain. I've also read Enigma by Hugh Sebag-Montefiore and managed to follow the methods explained there so I hope the fault is not all mine.
On the plus side, this book contains much more than just details on how the codes were cracked. There are many chapters on the development of intelligence gathering, intercepting signals and the politics, both national and international, involved. There is much information about the personnel too, not just the well known codebreakers, and explanations of the work of the less glamorous departments.
In summary this was full of fascinating information and was mostly well written, but if you're looking for detailed explanations on the methods of Turing et al. this is probably not that book.
April 18, 2017
Secret war
A collection of essays about Bletchley Park during the Second World War.
The most entertaining one is by the late John Chadwick.
This is how he describes his arrival in Heliopolis following the evacuation of Alexandria in 1942:
He was later promoted “Temporary Sub-Lieutenant (Special Branch) RNVSR” because the material he handled was classed ‘Officers Only’.
Later, after the Italian Armistice, he wanted to promote code discipline in the Aegean:
Chadwick later deciphered Linear B along with Michael Ventris.
A collection of essays about Bletchley Park during the Second World War.
The most entertaining one is by the late John Chadwick.
This is how he describes his arrival in Heliopolis following the evacuation of Alexandria in 1942:
My arrival created administrative chaos, since I was a lone naval rating attached to an Army Intelligence Unit, itself attached to an RAF station.
He was later promoted “Temporary Sub-Lieutenant (Special Branch) RNVSR” because the material he handled was classed ‘Officers Only’.
Later, after the Italian Armistice, he wanted to promote code discipline in the Aegean:
[…] I volunteered to go on the next mission to act as liaison with the Italian Navy in Leros, in the hope of preventing any further breaches of security. My suggestion was rejected, and I was told brutally that my superiors did not mind if I were killed, but they were unwilling to take the risk of my being taken prisoner.
Chadwick later deciphered Linear B along with Michael Ventris.
November 12, 2019
Each chapter/essay is by a different participant in the British codebreaking world of WWII, which makes the book anecdotal and sometimes repetitive. One needs prior knowledge of codebreaking techniques and related jargon to appreciate the whole. I abandoned p.170
June 16, 2025
impossible to understand in some parts. the historical chapters and first-hand accounts were well written, but the explanations on how the codes were actually broken and the set-up of the various machines was very poorly done. it was almost as if the writers did not care to consider whether the readers understood what they said (shockingly enough, the majority of the audience has not been working on ciphers for decades).
i may have just been out of my depth, but to put my complains into perspective, there was only one measly diagram explaining how enigma was set up in a highly complex and roundabout 400 page book.
alan turing himself could not have deciphered this novel.
i may have just been out of my depth, but to put my complains into perspective, there was only one measly diagram explaining how enigma was set up in a highly complex and roundabout 400 page book.
alan turing himself could not have deciphered this novel.
May 26, 2025
Thank you to everyone who worked tirelessly at Bletchley Park, you are unsung heroes, so many of you kept the roles you played a secret for years. With these books your stories are being told. We owe you so much, thank you again we would not have won the war without you.
To Tommy Flowers for designing and building Colossus, Alan Turing for his contribution. Generating new technologies and computers you lead the way. Thank you.
If you get the chance Bletchley Park is well worth the visit.
To Tommy Flowers for designing and building Colossus, Alan Turing for his contribution. Generating new technologies and computers you lead the way. Thank you.
If you get the chance Bletchley Park is well worth the visit.
April 28, 2018
Fascinating true account of code breaking and intelligence gathering and counter-intelligence from World War I through the Cold War.
March 24, 2017
Very much a book for those interested in the minutiae of the Enigma work and Bletchley park. Some accounts were interesting general reading, but most were too technical for my interest
July 8, 2016
Acknowledgements
Letter from the Bletchley Park codebreakers to Churchill
Dramatis Personae
--1. Bletchley Park in Pre-War Perspective, Christopher Andrew
--2. The Government Code and Cypher School and the First Cold War, Michael Smith
--3. Reminiscences on the Enigma, Hugh Foss
--4. Breaking Air Force and Army Enigma, Ralph Erskine
--5. Hut 6 From the Inside, Derek Taunt
--6. Breaking Italian Naval Enigma, Mavis Batey
--7. A Biographical Fragment: 1942-5, John Chadwick
--8. An Undervalued Effort: How the British Broke Japan's Codes, Michael Smith
--9. Solving JN-25 at Bletchley Park: 1943-5, Edward Simpson
--10. Most Helpful and Co-operative: GC&CS and the Development of American Diplomatic Cryptanalysis, 1941-2, David Alvarez
--11. Breaking German Naval Enigma on Both Sides of the Atlantic, Ralph Erskine
--12. Hut 8 From the Inside, Rolf Noskwith
--13. Bletchley Park and the Birth of the Very Special Relationship, Stephen Budiansky
--14. Mihailović or Tito? How the Codebreakers Helped Churchill Choose, John Cripps
--15. Traffic Analysis: A Log-reader's Tale, James W. Thirsk
--16. Bletchley Park, Double Cross and D-Day, Michael Smith
--17. How Dilly Knox And His Girls Broke the Abwehr Enigma, Keith Batey
--18. Breaking Tunny and the Birth of Colossus, Shaun Wylie
--19. Colossus and the Dawning of the Computer Age, B. Jack Copeland
--20. Enigma's Security: What the Germans Really Knew, Ralph Erskine
--21. From Amateurs to Professionals: GC&CS and Institution-Building in Signals Intelligence, Philip H. J. Davies
--22. Cold War Codebreaking and Beyond: the Legacy of Bletchley Park, Richard J. Aldrich
--23. Bletchley Park in Post-War Perspective, Christopher Andrew
Appendix I: The very simple cipher which 'Snow', the first Double Cross agent, was given by his German controllers
Appendix II: Wehrmacht Enigma Indicating Systems, except the Kriegsmarine's Kenngruppenbuch System
Appendix III: The Naval Enigma Kenngruppenbuch Indicator System - used with the main wartime ciphers
Appendix IV: Cillies
Appendix V: Enciphering by JN-25
Appendix VI: Recovery by Differencing
Appendix VII: Bayes, Hall's Weights and the Standardising of Judgements
Notes and References
Glossary and Abbreviations
Notes on Contributors
Index
Letter from the Bletchley Park codebreakers to Churchill
Dramatis Personae
--1. Bletchley Park in Pre-War Perspective, Christopher Andrew
--2. The Government Code and Cypher School and the First Cold War, Michael Smith
--3. Reminiscences on the Enigma, Hugh Foss
--4. Breaking Air Force and Army Enigma, Ralph Erskine
--5. Hut 6 From the Inside, Derek Taunt
--6. Breaking Italian Naval Enigma, Mavis Batey
--7. A Biographical Fragment: 1942-5, John Chadwick
--8. An Undervalued Effort: How the British Broke Japan's Codes, Michael Smith
--9. Solving JN-25 at Bletchley Park: 1943-5, Edward Simpson
--10. Most Helpful and Co-operative: GC&CS and the Development of American Diplomatic Cryptanalysis, 1941-2, David Alvarez
--11. Breaking German Naval Enigma on Both Sides of the Atlantic, Ralph Erskine
--12. Hut 8 From the Inside, Rolf Noskwith
--13. Bletchley Park and the Birth of the Very Special Relationship, Stephen Budiansky
--14. Mihailović or Tito? How the Codebreakers Helped Churchill Choose, John Cripps
--15. Traffic Analysis: A Log-reader's Tale, James W. Thirsk
--16. Bletchley Park, Double Cross and D-Day, Michael Smith
--17. How Dilly Knox And His Girls Broke the Abwehr Enigma, Keith Batey
--18. Breaking Tunny and the Birth of Colossus, Shaun Wylie
--19. Colossus and the Dawning of the Computer Age, B. Jack Copeland
--20. Enigma's Security: What the Germans Really Knew, Ralph Erskine
--21. From Amateurs to Professionals: GC&CS and Institution-Building in Signals Intelligence, Philip H. J. Davies
--22. Cold War Codebreaking and Beyond: the Legacy of Bletchley Park, Richard J. Aldrich
--23. Bletchley Park in Post-War Perspective, Christopher Andrew
Appendix I: The very simple cipher which 'Snow', the first Double Cross agent, was given by his German controllers
Appendix II: Wehrmacht Enigma Indicating Systems, except the Kriegsmarine's Kenngruppenbuch System
Appendix III: The Naval Enigma Kenngruppenbuch Indicator System - used with the main wartime ciphers
Appendix IV: Cillies
Appendix V: Enciphering by JN-25
Appendix VI: Recovery by Differencing
Appendix VII: Bayes, Hall's Weights and the Standardising of Judgements
Notes and References
Glossary and Abbreviations
Notes on Contributors
Index
November 28, 2014
Fascinating look inside the place my mother worked. We never knew this until the book the Ultra Secret was published. She never even told my Father. I think the sad thing about Bletchley park is unlike many of the American efforts that women aided in the women never get any credit because all they did was Take Down Messages. As the son of one of those message takers I can tell you they didn't break the codes but their input was invaluable to those who did. They could tell when operators changed or machines changed by reading the sender.
March 22, 2020
This is a great book, but can be hard going at times. Have reached the conclusion this is an occasional book - each chapter is a seperate discussion and can be read in isolation.
Some great insights into what went on at Bletchley Park
Some great insights into what went on at Bletchley Park
August 11, 2011
Complete, yet dull, background to the development of world war two code breaking technology.
April 24, 2013
after seeing the commercial for the television show on WETA, I thought I would look it up & sure enough it was there on Amazon ! if I could give it 10 stars I would !! HAZZAH!
February 10, 2014
Must read if you are interested in history, mathematics, and Cryptology.
Displaying 1 - 17 of 17 reviews