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² Livy xxvii, xliii, 1–8.

³ (1851).

⁴ David, Kahn, The codebreakers: the story of secret writing (New York, 1967), passim.Google Scholar

⁵ Ibid. pp. 298–9.

⁶ Christopher Andrew, ‘Déchiffrement et diplomatic: le cabinet noir du Quai d'Orsay sous la Troisième République’, Relations Internationales, III (1976), 37–64; Marcel Givierge, ‘Etude historique sur la Section du Chiffre’, Epoques 1–4, N.A.F. 24353, Departement des Manuscrits, Bibliothèque Nationale, Paris.

⁷ Francois, Carrier, ‘Le service d'écoute pendant la guerre’, Radio-Electricité, iv (1923), 453–60, 491–8 at p. 498.Google Scholar

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⁹ Russia (1923-, U.S.S.R.), Kommissia po izdaniu dokumentov epokhi imperializma, Die Internationalen Beziehungen im Zeitalter des Impmalismus: Dokumente aus den Archiven da Zarischen and der Provisorischen Regierung, ed. M. N. Pokrowski, German ed. Otto Hoetzsch (Berlin, 1931–42), passim, shows that Russia intercepted and solved diplomatic messages of England, France, Germany, Austria, Italy, Bulgaria, Turkey, Persia, and Greece before World War I. For police codebreaking, Richard J. Johnson, ‘Zagranichaia Agentura: the tsarist political police in Europe’, Journal of Contemporary History, vii (1972), 221–42; Kahn, The codebreakers, pp. 618–21.Google Scholar

¹⁰ Erich, Ludendorff, Ludendorffs own story (New York, 1919), 1, 57–8.Google Scholar

¹¹ Major [Kunibert] Randewig, ‘Die deutsche Funkaufklarung in der Schlacht bei Tannen-berg’, F-Flagge (magazine of German army signal troops) (1936), pp. 135–8, 154–7 at p. 135.

¹² Arthur Schuetz (pseud. Tristan Busch), Secret service unmasked, trans. Anthony, V. Ireland (London, [1948]), p. 58Google Scholar; Nicholas N. Golovine, The Russian campaign of 1914, trans. A. G. S. Muntz (Fort Leavenworth, 1933), pp. 171–2; Germany, Reichsarchiv, , Der Weltkrieg: 1914 bis 1918, II (Berlin, 1925), p. 351.Google Scholar

¹³ Max, Hoffmann, War diaries and other papers, trans. Eric Sutton (London, 1929), II, 267.Google Scholar

¹⁴ Ibid. 1, 41, 18.

¹⁵ Ronge, passim; Yves, Gylden, The contribution of the cryptographic bureaux in the World War, trans. Military Intelligence Division (Washington, 1935), pp. 60–77.Google Scholar

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¹⁷ Odoardo, Marchetti, Il servizio informazione dell'esercito italiano nella grande guerra (Roma, 1937), p. 181.Google Scholar

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¹⁹ ‘ConferencedeM. Georges Jean Painvin’, Bulletin de l'A.R.C. (Amicale des Reservistes du Chiffre), new series, vIII (1961), 5–47, at pp. 17–45; Kahn, The codebreakers, pp. 339–47.

²⁰ Henri, Morin, Service secret: à l'écoute devant Verdun, ed. Pierre, Andrieu (Paris, 1959), passimGoogle Scholar; Hermann, Cron, Die Organisation des deutschen Heeres im Weltkrieg, Forschungen and Darstellungen aus dem Reichsarchiv, v (Berlin, 1923), 112Google Scholar; Albert Praun, Soldat in der Telegraphen- and Nachrichtentruppe (Wurzburg, [c. 1965]), pp. I8–20, 26; Maximilian Ronge, ‘Der Telephon-Abhorchdienst’, pp. 670–729, and Beilagen, Nachlass B/126: F.2, Kriegsarchiv.

²¹ Priestley, R. E., The signal service in the European War of 1914 to 1918 (France) ([London?], 1921), p. 106.Google Scholar

²² Sir Alfred Ewing,'some special war work’, in Jones, R. V., ‘Alfred Ewing and “Room 40”‘, Notes and Records of the Royal Society of London, xxxiv (July 1979), 65–90CrossRefGoogle Scholar; Churchill, Winston S., The world crisis (New York, 1923), 1, 503–4Google Scholar; William James, Admiral Sir, The eyes of the navy: a biographical study of Admiral Sir William Hall (London, 1956), passim.Google Scholar

²³ Barbara, Tuchman, The Zimmermann telegram (New York, 1958)Google Scholar; William F. Friedman and Charles J. Mendelsohn, The Zimmermann telegram of January 16, 1917 and its cryptographic backgroand (1938, reprinted Laguna Hills, Calif, 1977); Kahn, The codebreakers, pp. 282–97.

²⁴ David, Kahn, Hitler's spies: German military intelligence in World War II (New York, 1978), pp. 185, 190–91, 214Google Scholar; Hinsley, F. H. with Thomas, E. E., Ransom, C. F. G. and Knight, R. C., British intelligence in the Second World War: its influence on strategy and operations (London, 1979.), 1, 20Google Scholar; Christopher Andrew, ‘The British Secret Service and Anglo-Soviet relations in the 1920s. Part I: From the trade negotiations to the Zinoviev letter’, Historical Journal, xx (1977), 673–706 at p. 680Google Scholar; Yardley, Herbert O., The American Black Chamber (Indianapolis, 1931), pp. 239–40.Google Scholar

²⁵ Kahn, The codebreakers, pp. 394–426.

²⁶ U.S. Patent 1,657,411; Siegfried, Tiürkel, Chiffrieren mil Geräten and Maschinen (Graz, 1927), pp. 71–94 and plates M-PGoogle Scholar; Handbuch der Deutschen Akticn-Gesellschqften (Berlin, 1935), v, 6610.Google Scholar

²⁷ [Marian Rejewski], ‘ Enigma 1930–1940; Metodi i historia rozwiazania niemieckiego szyfru maszynowego (w zarysie)’ (unpublished; in private collection), p. 1; Jürgen, Rohwer, The critical convoy battles of March 1943: the battle for HX. 229/SC122, trans. Derek Masters (London, 1977). p. 231.Google Scholar

²⁸ Kahn, The codebreakers, pp. 426–7; memorandum, Y7858/437/G/39, signed E.N.T. (Edward N. Travis), 21 July 1939, FO 850/4/X?J3968, Public Record Office, London, mentions the Royal Air Force's Type-X machine.

²⁹ Memorandum of 29 Nov. 1937 in OKW: Wi/IF 5.2150, Bandesarchiv/Militararchiv, Freiburg-im-Breisgau; Thomas H. Dyer (U.S. Navy cryptanalyst), interview, 12 Dec. 1963.

³⁰ Willi Jensen, ‘Hilfegeräte der Kryptographie’, Dissertation (withdrawn), Fliensburg, 1955; Brian Randall, The Colossus, Technical Report Series, no. 90., Computing Laboratory, University of Newcastle-upon-Tyne (Newcastle, 1976); Brian, Johnson, The Secret War (London, 1978), pp 327–49.Google Scholar

³¹ Among the better known are those recounted in Yardley, The American Black Chamber, pp. 289–317, and Ullman, Richard H., The Anglo-Soviet accord (Princeton, 1973), pp. 267–310.Google Scholar

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³³ Kurt Vetterlein (engineer in charge of the intercept post), interview, 1 Sept. 1967; transcripts of intercepts in Inland II geheim, Vol. 477 f, Politisches Archiv, Auswartiges Amt, Bonn; Germany, Oberkommando der Wehrmacht, Wehrmachtfuhrungsstab, Kriegstagebmh... 1940–1945, ed. Percy Ernst Schramm (Frankfurt, 1961–9), III, 854; Walter, Schellenberg, The labyrinth: memoirs of Walter Schellenberg, trans. Louis Hagen (New York, 1956), p. 366.Google Scholar

³⁴ [Kunibert] Randewig, ‘Taktische Funkpeiling’, Wehrtechnische Hefte, 52 (1955), pp. 104–10; Randewig, ‘Verfahren der Funkaufklärung-Empfangs- and Peildienst-Auswertung’, in Albert Praun (ed.), ‘Eine Untersuchung über den Funkdienst des russischen, britischen and amerikan-ischen Heeres im zweiten Weltkrieg vom deutschen Standpunkt aus, unter besonderer Berück-sichtigung ihrer Sicherheit’, 18 Feb. 1950 (unpublished; in private collection); reports of radio reconnaissance units in Heeresgruppe Nord, 74130/28, Bandesarchiv/Militärarchiv; Herbert Schmidt (radio direction finder), interview, 30 Jan. 1970; Fritz Neeb (operating head of Army Group Centre radio intelligence), interview, 30 Dec. 1972.

³⁵ Report of 14 Mar. 1942, Armeeoberkommando 11, 22279/3, Bandesarchiv/Militärarchiv; report of 19 Jan. 1942,24. Infanterie Division, 22006/11, Bandesarchiv/Militärarchiv; report of 25 Feb. 1944, III. Panzer Korps, 53975/5, Bandesarchiv/Militärarchiv.

³⁶ Report of 1 Mar. 1944, p. 9, Heeresgruppe Nord, 75130/31, Bandesarchiv/Militärarchiv.

³⁷ Reports at pp. 107 and II0, Heeresgruppe D, 85459, Bandesarchiv/Militärarchiv; United States, War Department, Military Intelligence Division, German operational intelligence: a study of German operational intelligence, produced at German Military Documents Section by a combined British, Canadian, and U.S. Staff, (n.p., April, 1946), pp. 8–9, 24.

³⁸ Kahn, The codebreakers, p. 472, errs in saying that the Germans obtained the code from the Italians, who had stolen it from the American embassy in Rome and were reading Feller's messages themselves (General Cesare Amè, Guerra segreta in Italia 1940–43 [Rome, 1954], pp. 96–8). The Germans solved it themselves.

³⁹ Wilhelm F. Flicke, War secrets in the ether, trans. Ray Pettengill, W. (Washington, 1953, reprinted with emendations, Laguna Hills, Calif, 1977), II, 192–8; Herbert Schaedel (archivist for the ChiffrierabteilungoftheOberkommandoderWehrmacht), interview, 29 July 1969; Anton Staubwasser (British specialist in the German army high command's Foreign Armies West), interview, 9 Mar. 1970.Google Scholar

⁴⁰ Hans-Otto Behrendt (assistant intelligence officer to Rommel at the time), interview, 18 Nov. 1978.

⁴¹ [Adolf, Hitler], Hitlers Tischgespräche im Führerhauptquartier 1941–1942, ed. Henry, Picker, new ed. Percy Ernst, Schramm (Stuttgart, 1963), transcript for 29. Juni 1942 abends.Google Scholar

⁴² Flicke, War secrets in the ether, p. 197.

⁴³ Ulrich Liss, ‘Der entscheidende Wert richtiger Feindbeurteilung - I: Beispiele aus der neueren Kriegsgeschichte’, Wehrkande, vIII (Nov. 1959), 584–92 at p. 585.

⁴⁴ Reinhard Gehlen et al.’ The German G-2 Service in the Russian Campaign (Ic-DienstOst)’, 1st Special Intelligence Interrogation Report, Interrogation Center United States Forces European Theater (22 July 1945), p. 16.

⁴⁵ Karl Dönitz, letter, 27 Jan. 1970.

⁴⁶ Heinz Bonatz, Die deutsche Marine-Funkaufklärung 1914–1945 (Beiträge zur Wehrforschung, xx/xxi) (Darmstadt, 1970), p. 138; Jürgen Rohwer, ‘La Radiotelegraphie: Auxiliare du commandement dans la guerre sous-marin’, Revue d'histoire de la deuxième guerre mondiale, XVIII (Jan. 1968), 41–66 at p. 52.

⁴⁷ B-Dienst war diary, p. 78, III M 1006/6, Bandesarchiv/Militärarchiv; Wilhelm Tranow (technical head of the B-Dienst), interview, 1 July 1970.

⁴⁸ Rohwer, The critical convoy battles of March 1943, pp. 240, 51, 61.

⁴⁹ B-Dienst war diary, p. 169, III M 1006/6, Bandesarchiv/Militärarchiv.

⁵⁰ Walther Seifert (head of evaluation for the Forschungsamt, Göring's codebreaking and wiretapping agency), interview, 19 Aug. 1970; ‘Die Vernehmung von Generaloberst Jodl durch die Sowjets’, trans. Wilhelm Arenz, Wehrwissenschaftliche Randschau, II (Sept. 1961), 534–42 at p. 539.

⁵¹ Report of 10 Oct. 1944, p. 1, in Heeresgruppe C, 75138/31, Bandesarchiv/Militärarchiv.

⁵² Dyer interview; Wesley A. Wright (navy cryptanalyst in Pearl Harbor), interview, 12 Dec. 1963. Additional first-person material in Holmes, W. J., Double-edged secrets: U.S. naval intelligence operations in the Pacific during World War II (Annapolis, 1979)Google Scholar, and Rhoer, Edward Van Der, Deadly magic: a personal account of communications intelligence in World War II in the Pacific (New York, 1978).Google Scholar

⁵³ Dyer interview.

⁵⁴ Chester W. Nimitz and E. B. Potter (eds.), The Great Sea War: the story of naval action in World War II (Englewood Cliffs, NJ., 1960), p. 245.

⁵⁵ Letter to presidential candidate Thomas E. Dewey, 27 Sept. 1944, in United States, Congress, Joint Committee on the Investigation of the Pearl Harbor Attack, Pearl Harbor Attack, Hearings, 79th Congress, 1st and 2nd Sessions (Washington, 1946), part 3, pp. 1132–3 at p. 1132.Google Scholar

⁵⁶ Charles A. Lockwood (commander of U.S. submarines in the Pacific), letter, 25 Nov. 1964. See also United States, Navy, Chief of Naval Operations, OP-20-G-7,’ The role of communications intelligence in submarine warfare in the Pacific (January 1943-October, 1943)’, 19 Nov. 1945, SRH-0II, Record Group 457, National Archives, and Clay Blair, Jr., Silent Victory: The U.S. submarine war against Japan (Philadelphia, 1975).Google Scholar

⁵⁷ Cited in Nimitz and Potter, The Great Sea War, pp. 422–3.

⁵⁸ Burke, Davis, Get Yamamoto (New York, 1969); Holmes, Double-edged secrets, pp. 135–6.Google Scholar

⁵⁹ Various sources. Kahn, The codebreakers, p. 19, errs in implying that the PURPLE machine used rotors. The suggestion that PURPLE was similar cryptographically to the Enigma and thus owed its solution to the Enigma solution has been educed from this Kahn error and is itself false. The solutions were entirely independent of one another.

⁶⁰ Pearl Harbor attack, part 36, p. 312, part 34, p. 84.

⁶¹ United States, War Department, Office of Assistant Chief of Staff, G-2, ‘MAGIC Summaries’, 20Mar.to31 Dec. 1942, NC3–457–78–4, and’MAGIC Diplomatic Summaries’, 1943, NC3–457–78–7, both Record Group 457, National Archives.

⁶² ‘“MAGIC” Summary’, no. 562 of 9 Oct. 1943 in ‘MAGIC Diplomatic Summaries’. This meeting, incidentally, is not included in Andreas Hillgruber (ed.), Staatsmänner and Diplomaten bei Hitler; Vertrauliche Aufzeichnungen über Unterredungen mit Vertretem des Auslandes, 2. Teil, 1942–1944 (Frankfurt, 1970). The intercepts thus include reports of Hitler conversations that seem not to exist in the German archives and so constitute a useful new source for the history of Hitler's Reich.

⁶³ ‘“MAGIC” Summary’ of 17 Dec. 1943, in ‘MAGIC Diplomatic Summaries’.

⁶⁴ Pearl Harbor attack, part 3, p. 1132.

⁶⁵ Johnson, The Secret War, p. 310; Stefan Korbonski, ‘The true story of Enigma - the German code machine in World War II’, East European Quarterly, xI (Summer 1977), 227–34 at P. 228.

⁶⁶ [Rejewski], ‘Enigma 1920–1930’, §1.

⁶⁷ Gustav, Bertrand, Enigma: ou le plus grand énigmt de la guerre 1939–1945 (Paris, 1973), p. 29; Gustav Bertrand (in charge of French cryptographic espionage), interview, 12 July 1974; Walther Seifert, telephone interview, 12 July 1974; [Rejewski], ‘Enigma 1920–1930’, §4.Google Scholar

⁶⁸ [Rejewski],’ Enigma 1920–1930’, §22. See also Richard A. Woytak, On the border of peace and war: Polish intelligence and diplomacy in 1937–1939 and the origins of the Ultra secret (Boulder, 1979).

⁶⁹ Bertrand, Enigma, pp. 59–60.

⁷⁰ Penelope, Fitzgerald, The Knox brothers, (New York, 1977), passim.Google Scholar

⁷¹ Ronald, Lewin, Ultra goes to war (New York, 1978), pp. 112–13.Google Scholar

⁷² Hinsley et al. British intelligence, pp. 178–9.

⁷³ Ibid. pp. 528–48; Evans, N. E.,‘ Air intelligence and the Coventry raid’, Royal United Services Institution Journal (Sept. 1976), 66–73.Google Scholar

⁷⁴ H. R. Trevor-Roper (a solver with E. W. B. Gill of the hand ciphers), interview, 1972; Werner Trautman (head of Abwehr radio station in Hamburg), interview, 20 Aug. 1970; Kim, Philby, My private war (New York, 1968), p. 65; Hinsley et al., British intelligence, p. 120.Google Scholar

⁷⁵ John, Masterman, The double-cross system in the War of 1939 to 1945 (New Haven, 1972), passim; Kahn, Hitler's spies, ch. 26.Google Scholar

⁷⁶ Rohwer, The critical convoy battles of March 1943, p. 238; Patrick, Beesly, Very special intelligence (London, 1977), pp. 70–1; Hinsley et al., British intelligence, pp. 336–7.Google Scholar

⁷⁷ Beesly, Very special intelligence, pp. II0-II, 64–5; Jürgen Rohwer, diagram ‘Development of German cipher-circles for Funkschliissel M (naval Enigma)’, in Newsletter of the American Committee on the History of the Second World War, no. 17 (May 1977), p. 5.

⁷⁸ Beesly, Very special intelligence, pp. 152–3.

⁷⁹ Ibid. pp. 176–7; Rohwer, The critical convoy battles of March 1943, p. 235.

⁸⁰ Beesly, Very special intelligence, pp. 200–1.

⁸¹ United States, Army, 6824 Detailed Interrogation Center, (MIS)M. 1121, ‘Information on German Secret Teletypewriters’, Record Group 165, National Archives; U.S. Patent No. 1,912,983; Hans Rohrbach,’ Chiffrierverfahren der neusten Zeit’, Archiv der elektrischen Ubertragung, 2 (Dec. 1948), 362–9 at §13.

⁸² Randall, The Colossus.

⁸³ Lewin, Ultra goes to war, pp. 325–6 [United States, Army], Memorandum for Colonel [Telford] Taylor, ‘Ultra and the U.S. Seventh Army’, 12 May 1945, SRH-022, Record Group 457, National Archives. See also Bennett, R., Ultra goes west (London, 1979).Google Scholar

⁸⁴ Memorandum for Colonel Taylor, ‘Ultra and the U.S. Seventh Army’, p. 2.

⁸⁵ Lewin, Ultra goes to war, pp. 336–40.

⁸⁶ According to records in the Berlin Document Center, the technical heads of the OKW Chiffrierabteilung (Wilhelm Fenner) and of the B-Dienst (Wilhelm Tranow) were not party members; Tranow wrested this post from an old party member (Lothar Franke, membership no. 19,852). The Foreign Office codebreaking unit's administrative head (Kurt Selchow) joined after the start of the war (1 Jan. 1940, membership no. 7,910,928); of his three main assistants, two were party members, one early (Adolf Paschke, 1 May 1933, 2,649,870), and one late (Rudolf Schauffler, 1 Jan, 1942, 8,743,951), and one was not (Werner Kunze). The leading officials of the Forschungsamt, Goring's wiretapping and codebreaking agency, were all Nazis.

⁸⁷ Seifert, interview.

⁸⁸ Leo Hepp, ‘Das Grösste Geheimnis des Zweiten Weltkrieges?’, Wehrkande (1976), pp. 86–9 at 88–9; Dr Erich Hüttenhain (in charge of German cipher systems in OKW Chiffrierabteilung), letter, 15 Feb. 1979.

⁸⁹ This section, especially the part dealing with the technical reasons, owes a great deal to Dr C. A. Deavours, professor of mathematics at Kean College of New Jersey, who has thoroughly investigated the cryptology of the Enigma. I am deeply grateful to him for his help. The section has also benefited from the following people, who read it in draft and commented upon it: Dr I. J. Good, one of the team who worked with Newman at Bletchley on the electronic cryptanalytical machines and is now University Distinguished Professor of Statistics at the Virginia Polytechnic Institute and State University; Dr Karl-Heinz Ludwig, professor at the University of Bremen and author of Tecknik and Ingenieure im Dritten Reich (Düsseldorf, 1974); Dr Henry A. Turner, professor of history at Yale University specializing in twentieth-century German economics; Dr Andreas Hillgruber, professor of history at Cologne University and a leading World War II historian; Heinz Bonatz, retired Kapitan zur See, head of the B-Dienst from 1934 to 1936 and from 1942 to 1944; Dr Erich Hüttenhain; and Dr Alan Beyerchen, professor of history at the Ohio State University and author of Scientists ander Hitler: politics and the physics community in the Third Reich (New Haven, 1977).Google Scholar

⁹⁰ Milward, Alan S., War, economy and society 1939–45 (Berkeley, 1977), pp. 169–193, discusses similar problems in a broader context.Google Scholar

⁹¹ Tadeusz Lisicki, ‘The achievement of the Polish Biuro Szyfrów in breaking the German Enigma cipher’, talk delivered before the Arbeitskreis für Wehrforschung, Bonn, 15 Nov. 1978.

⁹² Another general reason might seem to be that the Allies' larger population would have given them more, and probably better, people for codebreaking. But it is not known how many of the approximately 10,000 people at Bletchley were solving ciphers other than German at any particular time or how many in the German agencies were solving Soviet, Italian, Japanese, Turkish, Swedish, and other non-U.S. and non-U.K. systems at the same time. Moreover, the contributions of other governments - Canadian, Free French, Dutch, Italian, Japanese, Hungarian - to their respective allies cannot readily be measured in terms of manpower. Finally, the number of persons in field units, both Allied and German, is not known with precision. I myself have the feeling that more people in the West attacked German ciphers than worked in Germany on Allied ciphers and so I think that greater Allied population probably did contribute to greater success. But, lacking the figures that would prove or disprove this conjecture, I do not advance it. A corollary to this would be that the Allies' greater industrial capacity enabled them to help both their codebreakers and their codemakers more. But this help would have been so small in relation to either the Allied or the Axis war effort as to be insignificant. So this cannot be adduced as a factor, either.

⁹³ Kahn, Hitler's spies, pp. 172–222, esp. p. 176.

⁹⁴ Ibid. pp. 534–6.

⁹⁵ This is developed in more detail in ibid. pp. 528–31.

⁹⁶ Carl von Clausewitz, On War, trans, and ed. Michael Howard and Peter Paret (Princeton, 1976), book vi, chapter 1.

⁹⁷ Ibid, book vII, chapter 2.

⁹⁸ Georges, Castellan, Le réarmament clandestin du Reich, 1930–1935, vu par le 2e bureau de l'état-major frartfais (Paris, 1954); Bonatz, Die deutsche Marine-Funkaufklärung, p. 93.Google Scholar

⁹⁹ Hinsley et al., British intelligence, pp. 12–13, 36–43; Kahn, Hitler's spies, pp. 54, 387–8, 393–8.

¹⁰⁰ Solomon Kullback, telephone interview, 2 Oct. 1978.

¹⁰¹ Tranow, interviews. The book was Roger Baudouin's Elements de cryptographic (Paris, 1939).Google Scholar

¹⁰² w. Preston Corderman (a first student in this school, later wartime head of the U.S. Army codebreaking agency), interview, 2 Nov. 1976; Friedman, W. F., Military cryptanalysis (Washington, 1938–42).Google Scholar

¹⁰³ United States, War Department, Technical Manual 11–380, Converter M-209 (27 Apr. 1942), §5b.

¹⁰⁴ See, for example, Germany, Oberkommando der Wehrmacht, Heeresdienstvorschrift geheim 7 (also Marinedienstvorschrift 534, Luftwaffedienstvorschrift geheim 7), Allgemeine Schluesselregeln für die Wehrmacht, 1 Apr. 1944, and Germany, [Reichswehrministerium], Heeresdienstvorschrift geheim 13 (also Luftwaffedienstvorschrift geheim 13), Gebrauschsanleitung für die Chiffriermaschine Enigma, 12 Jan. 1937).

¹⁰⁵ Beyerchen, letter, 13 Apr. 1979, says that urgency stimulated the Allies to break down the barrier between theoretical and applied mathematicians and scientists and that the lack of urgency in Germany ‘left their peacetime barrier intact’.

¹⁰⁶ T. H. Flowers, letter, 13 Feb. 1979. I am deeply grateful to Mr Flowers for this letter and one of 18 Apr. 1979, which explain how the British advanced from electromechanical to electronic machines.

¹⁰⁷ Ibid.; I. J. Good, ‘Early work on computers at Bletchley’, Cryptologia, 3 (April, 1979), 65–77 at p. 73.

¹⁰⁸ Konrad Zuse (German computer pioneer), letters, 22 Nov. 1976 and 5 Jan. 1977.

¹⁰⁹ Bonatz, interview, 15 Nov. 1978.

¹¹⁰ See, for example, Max Pinl and Lux Furtmuller, ‘Mathematicians ander Hitler’, Leo Baeck Institute, year Book XVIII (London, 1973), 129—82.

¹¹¹ An attempt to trace the roots of German arrogance in Kahn, Hitler's spies, pp. 525–8.

¹¹² Beesly, Very special intelligence, pp. 57–8; Kahn, Hitler's spies, p. 533.

¹¹³ Kullback, interview.

¹¹⁴ Kahn, The codebreakers, p. 613; see alsoJürgen Rohwer,’ Die alliierte Funtauflärung and der Verlauf des Zweiten Weltkrieges’, Vierteljahrshefte fur Zeitgeschichte, XXVII (1979), 325–69.

¹¹⁵ Corderman, interview.

¹¹⁶ Harold Deutsch, talk at colloquium on ‘What role did radio intelligence play in the course of the Second World War?’, Stuttgart, 17 Nov. 1978.

¹¹⁷ See also David Kahn, ‘The Ultra conference’, Cryptologia, 3 (January, 1979), 1–8 at pp. 5–6.

¹¹⁸ Preface to Praun, ‘Eine Untersuchung... ‘.

¹¹⁹ Eisenhower to Menzies, 12 July 1945, Eisenhower Library, Abilene, Kansas.

¹²⁰ Pearl Irlarbor attack, part 3, p. 1133.