The Info List - Dilly's Rodding Method

--- Advertisement ---

Alfred Dillwyn "Dilly" Knox, CMG (23 July 1884 – 27 February 1943) was a British classics scholar and papyrologist at King's College, Cambridge and a codebreaker. As a member of the World War I
World War I
Room 40 codebreaking unit, he helped decrypt the Zimmermann Telegram
Zimmermann Telegram
which brought the USA into World War I.[1] He joined the GC&CS at the war's end.[2] As Chief Cryptographer,[2] Knox played an important role in the Polish-French-British meetings on the eve of World War II
World War II
which disclosed Polish cryptanalysis of the Axis Enigma to the Allies.[3] At Bletchley Park
Bletchley Park
he worked on the cryptanalysis of Enigma ciphers until his death in 1943. He built the team and discovered the method that broke the Italian Naval Enigma, producing the intelligence credited with Allied victory at the Battle of Cape Matapan. In 1941, Knox broke the Abwehr
Enigma.[4] By the end of the war, Intelligence Service Knox had disseminated 140,800 Abwehr
decrypts,[4] including intelligence important for D-Day.[5]


1 Personal life and family 2 Academic scholarship 3 Codebreaking

3.1 World War I 3.2 Between WW1 and WW2

3.2.1 Government Code and Cypher School 3.2.2 Commercial Enigma 3.2.3 Spanish Enigma 3.2.4 On the eve of World War II Polish-French-British meetings Turing's bombe

3.3 World War II

3.3.1 Knox's rodding method 3.3.2 Intelligence Services Knox 3.3.3 Death

4 Classified poetry 5 Portayals in fiction 6 Notes 7 References 8 Further reading

Personal life and family[edit] Dillwyn Knox, the fourth of six children,[6] was the son of Edmund Arbuthnott Knox, tutor at Merton College
Merton College
and later Bishop of Manchester; he was the brother of E. V. Knox, Wilfred Knox
Wilfred Knox
and Ronald Knox,[6] and uncle of the novelist Penelope Fitzgerald.[7] Dillwyn—known as "Dilly"—Knox was educated at Summer Fields School, Oxford, and then Eton College.[6] He studied classics at King's College, Cambridge
King's College, Cambridge
from 1903,[8] and in 1909 was elected a Fellow[6] following the death of Walter George Headlam, from whom he inherited extensive research into the works of Herodas. While an undergraduate he was friends with Lytton Strachey
Lytton Strachey
and John Maynard Keynes. Knox privately coached Harold Macmillan, the future Prime Minister at King's for a few weeks in 1910, but Macmillan found him "austere and uncongenial".[8] He married Olive Rodman in 1920, forgetting to invite two of his three brothers to his wedding.[9] The couple had two sons, Oliver and Christopher. He was an atheist.[10] Academic scholarship[edit] Between the two World Wars Knox worked on the great commentary on Herodas
that had been started by Headlam, damaging his eyesight while studying the British Museum's collection of papyrus fragments, but finally managing to decipher the text of the Herodas
papyri. The Knox-Headlam edition of Herodas
finally appeared in 1922.[11] Codebreaking[edit] World War I[edit]

The sailor in Room 53 has never, it's true, been to sea but though not in a boat he has served afloat — in a bath in the Admiralty.

— Alice in ID25
by Frank Birch[12]

Soon after World War I
World War I
broke out in 1914,[2] Knox was recruited to the Royal Navy's cryptological effort in Room 40
Room 40
of the Admiralty Old Building,[13] where some of his best work is said to have been done in the bath (in Room 53).[12] In 1917, Knox followed Room 40
Room 40
with its expansion into ID25.[2] Among other tasks, he was involved in breaking:

the Zimmermann Telegram
Zimmermann Telegram
which brought the USA into the war.[1] much of the German admiral's flag code by exploiting an operator's love of romantic poetry.[2]

Between WW1 and WW2[edit] Government Code and Cypher School[edit]

“ Oh, if a time should ever come when we're demobilized How we shall miss the interests which once life comprised!

— Dilly the Dodo[2], Alice in ID25
by Frank Birch

During World War I
World War I
he had been elected Librarian at King's College, but never took up the appointment. After the war Knox intended to resume his research at King’s, but was persuaded by his wife to remain at his secret work; indeed, so secret was this work that his own children had no idea, until many years after his death, what he did for a living, and his contribution to the war effort.[8] Commercial Enigma[edit] The Enigma machine
Enigma machine
became available commercially in the 1920s. In Vienna
in 1925,[14] Knox bought the Enigma 'C' machine evaluated by Hugh Foss in 1927 on behalf of GC&CS. Foss found "a high degree of security" but wrote a secret paper describing how to attack the machine if cribs — short sections of plain text — could be guessed.[3] When — a decade later — Knox picked up this work, he developed a more effective algebraic system (rodding) based on the principles described by Foss.[14] Spanish Enigma[edit] Germany Navy adopted Enigma in 1926, adding a plug-board ('stecker') to improve security. Nazi Germany
Nazi Germany
supplied non-steckered machines to Franco's Nationalists in the Spanish Civil War. On 24 April 1937, Knox broke Franco's Enigma[3] but knowledge of this breakthrough was not shared with the Republicans.[15] Soon afterwards, Knox began to attack signals between Spain and Germany encrypted using steckered Enigma machines.[3] On the eve of World War II[edit] Polish-French-British meetings[edit] GC&CS began to discuss Enigma with France's Deuxième Bureau in 1938, obtaining from the Bureau details of Wehrmacht Engima
Wehrmacht Engima
supplied by Asché
and signal intercepts, some of which must have been made in Eastern Europe. This led the French to disclose their links with Polish cryptographers.[3] Knox, Hugh Foss and Alastair Denniston represented GS&CS at the first Polish-French-British meeting at Paris in January 1939.[2] The Poles were under order to disclose nothing of importance at this time, leaving the British codebreakers disappointed. However Knox's description of his system of rodding impressed the Polish codebreakers, and they requested his presence at a second meeting.[3]

Knox grasped everything very quickly, almost quick as lightning. It was evident that the British had been really working on Enigma ... So they didn't require explanations. They were specialists of a different kind, of a different class. — Marian Rejewski[2]

Knox attended the second Polish-French-British conference, held on 25–26 July 1939 at the Polish Cipher Bureau facility (at Pyry, south of Warsaw, Poland). Here, the Poles began to disclose to their French and British allies their achievements in solving Enigma decryption.[16] Although Marian Rejewski, the Polish cryptographer and mathematician who solved the plugboard-equipped Enigma used by Nazi Germany, approached the problem through permutation theory (whereas Knox applied linguistics) a good personal relationship was quickly established at the conference. The good impression made by Rejewski on Knox played an important role in increasing recruitment of mathematicians to Bletchley Park.[2] Knox was chagrined — but grateful — to learn how simple was the solution of the Enigma's entry ring (standard alphabetical order).[16]

It was such an obvious thing to do, really a silly thing to do, that nobody, not Dilly Knox or Tony Kendrick or Alan Turing, ever thought it worthwhile trying it. — Peter Twinn[3]

After the meeting, he sent the Polish cryptologists a very gracious note in Polish, on official British government stationery, thanking them for their assistance and sending "sincere thanks for your cooperation and patience".[2] Enclosed were a beautiful scarf featuring a picture of a Derby winner and a set of paper 'batons'.[16]

I don't know how Knox's method was supposed to work, most likely he had hoped to vanquish Enigma with the batons. Unfortunately we beat him to it. — Marian Rejewski[2]

These 'batons' were known as rods to the British and had been used to solve the Spanish Enigma. Knox's rodding method was later used to break the Italian Naval Enigma.[2] Turing's bombe[edit] Alan Turing
Alan Turing
worked on Enigma during the months leading to the outbreak of World War II
World War II
in September 1939, and occasionally visited GC&CS's London HQ to discuss this problem with Knox. In the 1939 Registration, Turing was recorded in Naphill, staying with Knox and his wife. By November 1939, Turing had completed the design of the bombe — a radical improvement of the Polish bomba.[17] World War II[edit] Knox's rodding method[edit] To break non-steckered Enigma machines (those without a plugboard), Knox (building on earlier research by Hugh Foss[3]) developed a system known as 'rodding', a linguistic as opposed to mathematical way of breaking codes. This technique worked on the Enigma used by the Italian Navy[18] and the German Abwehr. Knox worked in 'the Cottage', next door to the Bletchley Park
Bletchley Park
mansion, as head of a research section, which contributed significantly to cryptanalysis of the Enigma.[6] Knox's team at The Cottage used rodding to decrypt intercepted Italian naval signals describing the sailing of an Italian battle fleet, leading to the Battle of Cape Matapan
Battle of Cape Matapan
in March 1941. Admiral John Godfrey, Director of Naval Intelligence credited the Allied victory at Matapan to this intelligence; Admiral Sir Andrew Cunningham, who had commanded the victorious fleet at Matapan, went to Bletchley to personally congratulate 'Dilly and his girls'.[2] Intelligence Services Knox[edit] In October 1941, Knox solved the Abwehr
Enigma.[4] Intelligence Services Knox (ISK) was established to decrypt Abwehr communications.[4]In early 1942, with Knox seriously ill, Peter Twinn took charge of running ISK[5] and was appointed head after Knox's death.[4] By the end of the war, ISK had decrypted and disseminated 140,800 messages.[4] Intelligence gained from these Abwehr
decrypts played an important part in ensuring the success of Double-Cross operations by MI5 and MI6, and in Operation Fortitude, the Allied campaign to deceive the Germans about D-Day.[5] Death[edit] Knox's work was cut short when he fell ill with lymphoma.[19] When he became unable to travel to Bletchley Park, he continued his cryptographic work from his home in Hughenden, Buckinghamshire, where he received the CMG.[20] He died on 27 February 1943.[20] A biography of Knox, written by Mavis Batey, one of 'Dilly's girls', the female codebreakers who worked with him, was published in September 2009.[21] Classified poetry[edit]

“ These have knelled your fall and ruin, but your ears were far away English lassies rustling papers through the sodden Bletchley day.

— Dilly Knox, Epitaph on Matapan to Mussolini[2]

Knox celebrated the victory at Battle of Cape Matapan
Battle of Cape Matapan
with poetry, which remained classified until 1978.[2] Portayals in fiction[edit] Knox is shown recruiting Alan Turing
Alan Turing
to Bletchley Park
Bletchley Park
in Hugh Whitemore's play, Breaking the Code (1986). In the 1996 television film, he is portrayed by Richard Johnson. Notes[edit]

^ a b Gannon 2011 ^ a b c d e f g h i j k l m n o Batey 2011 ^ a b c d e f g h Smith 2010 ^ a b c d e f Batey 2009, p. xi ^ a b c "Peter Twinn", The Daily Telegraph, London, 17 November 2004, retrieved 16 August 2015  ^ a b c d e Batey 2004 ^ Fitzgerald 2002 ^ a b c Richmond, John Classics
and Intelligence - ' Classics
Ireland' Volume 9 (2002) ^ Batey 2009, p. xii ^ "Dillwyn [Knox, son of an Evangelical bishop] was from his student years an unwavering atheist." Alan Hollinghurst, "The Victory of Penelope Fitzgerald" (a review of Hermione Lee, Penelope Fitzgerald
Penelope Fitzgerald
[a niece of Alfred Dillwyn Knox]: A Life, Knopf, 488 pp.), The New York Review of Books, vol. LXI, no. 19 (December 4, 2014), p. 8. (The article comprises pp. 8, 10, 12.) ^ Herodas
(2010), Hedlam, Walter; Knox, A. D., eds., The Mimes and Fragments, Hardpress, ISBN 978-1290531078  ^ a b Andrew 2011 ^ Goebel ^ a b Foss 2011 ^ Keeley 2008 States "Professor Denis Smyth, of the University of Toronto, an expert on Second World War intelligence operations, said that the British codebreaker Alfred Dilwyn Knox cracked the code of Franco's machine in 1937, but 'this information was not passed on to the Republicans'." ^ a b c Budiansky 2000, p. 95,96 ^ Copeland 2011, p. 313 ^ Carter, p. 1 ^ Sebag-Montefiore 2000, p. 350 ^ a b Fitzgerald 2002, pp. 249–250 ^ Batey 2009


Batey, Mavis (2004). Knox, (Alfred) Dillwyn (1884–1943). Oxford Dictionary of National Biography.  Batey, Mavis (2005), "Marian and Dilly", in Rejewski, Marian, Marian Rejewski, 1905–1980: Living with the Enigma Secret, pp. 67–74  Batey, Mavis (2009). Dilly: The Man Who Broke Enigmas. Dialogue. ISBN 978-1-906447-01-4.  Batey, Mavis (2011). "Chapter 6: Breaking Italian Naval Enigma". In Erskine, Ralph; Smith, Michael. The Bletchley Park
Bletchley Park
Codebreakers. Biteback Publishing. pp. 79–92. ISBN 978-1849540780.  (Updated and extended version of Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer Bantam Press 2001) Andrew, Christopher (2011). "Chapter 1: Bletchley Park
Bletchley Park
in Pre-War Perspective". In Erskine, Ralph; Smith, Michael. The Bletchley Park Codebreakers. Biteback Publishing. pp. 1–12. ISBN 978-1849540780.  (Updated and extended version of Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer Bantam Press 2001) Foss, Hugh (2011). "Chapter 3: Reminiscences on the Enigma". In Erskine, Ralph; Smith, Michael. The Bletchley Park
Bletchley Park
Codebreakers. Biteback Publishing. pp. 35–39. ISBN 978-1849540780.  (Updated and extended version of Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer Bantam Press 2001) Copeland, Jack (2011). "Chapter 19: Colossus and the Dawning of the Computer Age". In Erskine, Ralph; Smith, Michael. The Bletchley Park Codebreakers. Biteback Publishing. pp. 305–327. ISBN 978-1849540780.  (Updated and extended version of Action This Day: From Breaking of the Enigma Code to the Birth of the Modern Computer Bantam Press 2001) Budiansky, Stephen (2000), Battle of wits: The Complete Story of Codebreaking in World War II, Free Press, ISBN 978-0-684-85932-3  Carter, Frank, Bletchley Park
Bletchley Park
Technical Articles: Rodding (PDF), archived from the original (PDF) on 11 April 2007, retrieved 14 February 2015  Fitzgerald, Penelope (2002). The Knox Brothers. Flamingo. ISBN 978-0-00-711830-4.  Gannon, Paul (2011), Inside Room 40: The Codebreakers of World War I, London, UK: Ian Allen Publishing, ISBN 978-0-7110-3408-2  Goebel, Greg. "Codes, Ciphers, & Codebreaking". [4.1] Room 40 & the Zimmermann telegram/German codebreakers. Retrieved 14 February 2015.  Kahn, David (1991), Seizing the Enigma: The Race to Break the German U-boat Codes, 1939-1943, Houghton Mifflin Co., pp. 25–26, 84–85, ISBN 978-0-395-42739-2  Keeley, Graham (24 October 2008), "Nazi Enigma machines helped General Franco in Spanish Civil War", The Times, p. 27, retrieved 14 February 2015  Kozaczuk, Władysław (1984), Enigma: How the German Machine Cipher was Broken, and how it was Read by the Allies in World War Two - Edited and translated by Christopher Kasparek, Frederick, Maryland (a substantially revised and augmented translation of W kręgu enigmy, Warsaw, Książka i Wiedza, 1979, supplemented with additional appendices by Marian Rejewski.) (2 ed.), University Publications of America, ISBN 978-0-89093-547-7  Sebag-Montefiore, Hugh (2000), Enigma: The Battle for the Code, London, UK: Weidenfeld & Nicolson, ISBN 0-7538-1130-8  Smith, Michael (2010). "How It Began: Bletchley Park
Bletchley Park
Goes to War". Colossus: The Secrets of Bletchley Park's Codebreaking Computers. Oxford University Press. pp. 18–35. ISBN 978-0-19-957814-6.  Thorpe, D.R. (2010). Supermac: The Life of Harold Macmillan. Chatto & Windus.  "Peter Twinn", The Telegraph, London, UK, 17 November 2004, archived from the original on 2 March 2007, retrieved 14 February 2015 

Further reading[edit]


Batey, Mavis (2009). Dilly: The Man Who Broke Enigmas. Dialogue. ISBN 978-1-906447-01-4.  Fitzgerald, Penelope (2002). The Knox Brothers. Flamingo. ISBN 978-0-00-711830-4. 

Authority control

WorldCat Identities VIAF: 54530537 LCCN: n91125336 ISNI: 0000 0001 0903 0327 GND: 142834203 SUDOC: 032335695 BNF: cb123385199 (data) BIBSYS: 8082030 N