British codebreaking and American diplomatic telegrams, 1914–1915

Abstract

During the First World War, British intelligence solved the United States' diplomatic codes and were reading its diplomatic telegrams transmitted between Washington and US diplomatic outposts throughout Europe. Controversy has emerged over when the British succeeded in solving these codes, with two historians relatively recently having claimed that British intelligence succeeded in doing so from the beginning of the war or soon after. Through a thorough consideration of the available documentation, this piece aims to correct these mistaken claims and to date the completion of the British solving of American codebooks to the middle phase of the war, to between October 1915 and January 1916. It seeks to lay reliable foundations for further work by showing that research into the wartime impact of British signals’ intelligence on Anglo-American relations is necessarily limited to only the middle and later phases of the war.

Notes

1. Andrew and Dilks (eds.), The Missing Dimension.

2. Larsen, “Intelligence in the First World War.”

3. Gannon, Inside Room 40, 122; Lambert, Planning Armageddon, 263–64, 424.

4. Larsen, “British Intelligence”; Larsen, “War Pessimism in Britain”; Freeman, “MI1(b).”

5. Larsen, “British Intelligence.”

6. Ferris, “Before ‘Room 40’”; Ferris, “The Road to Bletchley”; Andrew, Secret Service, chs.1–2.

7. Andrew, Secret Service, ch.3; Beesly, Room 40; Gannon, Inside Room 40; Nicholas Hiley, “The Strategic Origins of Room 40.”

8. Ferris, “Before “Room 40’,” 443–444.

9. Official History of MI1(b), TNA: HW 7/35; R. H. Brade Memorandum No. 803, 12 April 1915, War Office Memorandum, 15 May 1915, War Office Organizational Chart [1915], NAM: Esher Papers, Acc. 2006-11-57, Vol.I; Ferris, “Before ‘Room 40’,” 444–445; Freeman, “MI1(b),” 207–210.

10. See Weber, ‘State Department Cryptographic Security,” 555–570; Weber, United States Diplomatic Codes and Ciphers, 241–248; Wrixon, Codes, Ciphers, Secrets, 337–44. See also Barker, ed., The History of Codes and Ciphers; Cipher of the Department of State [1918], GULL: MI-14863.

11. See NARA: Record Group 59, State Department Decimal File 1910–1929.

12. See note 10 above.

13. An exhaustive list is impractical here, but see for example and in particular, Link, Wilson: The Struggle for Neutrality; Devlin, Too Proud to Fight, chs.5–12; Lambert, Planning Armageddon, chs.6–10; Neu, Colonel House, chs.12–17.

14. Larsen, “British Intelligence.”

15. See Weber, “State Department,” 576–7; Link (ed.), Papers of Woodrow Wilson, vols.32, 300–1, 304, 328, 335, 372, 403, 422–23, 429, 455–56, 462, 475, 504, 521, 523–24, 531–32, vols.33, 10–11, 12–3, 63–4, 88–9, 105–06, 134, 190, 198, 205, 217, 222–23, 229, 239, 247–48, 253, 257, 266–67, 321.

16. Gannon, Inside Room 40, 122; cf. Larsen, “British Intelligence,” 690 n. 47.

17. TNA: WO 106/6072.

18. FRUS 1916, 253, 260, 266.

19. FRUS 1915, 942–43.

20. Appendix to Twentieth Report, TNA: ADM 137/2736.

21. Lambert, Planning Armageddon, 263–64.

22. Lambert, Planning Armageddon, 424.

23. Draft ‘D’, Chapter 25, Hall unpublished autobiography, CCAC, HALL 3/6; “Political Branch of Room 40” Memorandum, TNA: ADM 223/773; Gannon, Inside Room 40, ch.10; Beesley, Room 40, ch.8.

24. NAC: Record Group 25 f8, Volume 1073, File #81, [U.K.] Report on Cable Censorship during the Great War (1914–1919), 10; see, for example, Egan to State Department, 25 September 1916, NARA: Record Group 59, State Department Decimal File 1910–1929, 763.72119/172. See also Winkler, “Information Warfare in World War I”; Winkler, Nexus; Headrick, The Invisible Weapon, chs.8–9.

25. Appendix to Twentieth Report, TNA: ADM 137/2988; TNA: ADM 137/2736, WO 106/6072, HW 7/17. See also note immediately previous.

26. Page to Lansing, Telegram 2852, 23 September 1915, NARA: Record Group 59, State Department Decimal File 1910–1929, 763.72112/1615; FRUS 1915, 238; Intercept in TNA: ADM 137/2736. I am grateful to NARA archivist David Langbart for looking this up for me.

27. Bryan to Page, Telegram 1665, 7 June 1915, NARA: Record Group 59, State Department Decimal File 1910–1929, 763.72112/1560a; FRUS 1915, 225–26; Intercept in TNA: ADM 137/2736. I am grateful to NARA archivist David Langbart for looking this up for me.

28. America and the Blockade, TNA: ADM 137/2736.

29. Freeman, “MI1(b),” 210–11.

30. London to Washington Decrypt, 25 September 1915, TNA: WO 106/6072.

31. Official History of MI1(b), TNA: HW 7/35.

32. Office Memorandum No. 825, 29 January 1916, NAM: Esher Papers, Acc. 2006-11-57, Vol.I.

33. London to Washington Decrypt, 25 September 1915 TNA: WO 106/6072.

34. Page to Lansing, 25 September 1915, NARA: Record Group 59, State Department Decimal File 1910–1929, Box 363, 051.62/174; FRUS 1915, 942–43.

35. London to Washington Decrypt, [23 January 1916], TNA: HW 7/17, WO 106/6072; Freeman, “MI1(b),” 211, 226 n. 34.

36. London to Washington Intercept, 25 September 1915, TNA: WO 106/6072.

37. Weber, “State Department,” 572–576; Edward House Diary, 25 January 1915, YUL: House Papers; Larsen, “British Intelligence.”

38. Freeman, “MI1(b),” 210–12.

39. Official History of MI1(b), TNA: HW 7/35; Freeman, “MI1(b),” 212.