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Appendix B

Summary of Diplomatic Messages July-November 1941

After 24 November 1941, events in U.S.-Japanese diplomatic negotiations moved very swiftly to their climax on 7 December. A number of important diplomatic messages passed between Tokyo and Washington between July and November; these are summarized below. These early messages and those exchanged after 24 November which have been selected for inclusion in this appendix are so revealing that it is easy to lose sight of the fact that U.S. officials were often reading these messages at about the same time as the Japanese diplomats. The "War Warning" messages sent by OPNAV beginning on 24 November have also been included in this appendix to insure that the reader fully appreciates their correlation with events occurring in diplomatic circles.

  • Despite changes in its government, Japan remained committed to the Tripartite Pact with Germany and Italy.
  • Japan frequently expressed determination to use force against the United States and Great Britain.
  • Japan established an espionage network in the United States.
  • Plans for evacuation of Japanese diplomatic, espionage, and newspaper personnel were discussed.
  • Germany and Italy applied pressure on Japan to provoke war with the U.S.
  • Japanese attitude toward the U.S. Open Door policy hardened after 16 October when Tojo took over the government. Japan wanted the U.S. to approve Japanese policies in the Far East -- including China and French Indochina -- and restore Japanese trade status with the U.S.
  • Ambassador Nomura's attempt to resign on 22 October was refused.
  • On 4 November, Ambassador Saburo Kurusu, sent to help Nomura, was not optimistic that negotiations would be successful. He arrived in Washington on 17 November.
  • On 5 November, Tokyo established a 25 November deadline for completion of negotiations.
  • Nomura reported on 10 November on statements from high-ranking politicians and cabinet members (a) that the U.S. was not bluffing, (b) that it was ready for war, (c) that it had reliable reports that Japan would be on the move soon, and (d) that the president and secretary of state believed these reports.
  • On 19 November 1941, two messages from 15 November were read which discussed plans to evacuate Japanese citizens from the U.S.


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The messages which follow are arranged in order of transmission. Army messages are indicated with an "A" and Navy messages with an "N." The date given is the date the message was translated.

N 25 Nov A circular message from Tokyo to Washington on 15 November with detailed instructions on how to destroy code machines.
N 28 Nov A circular message from Tokyo to Washington on 19 November with detailed instructions to listen for "Winds Execute" messages to be added to Japanese news broadcasts in case of diplomatic emergencies involving the U.S., England, or Russia. When heard, embassies were to destroy all codes, papers, etc.
N 26 Nov A circular message from Tokyo to Washington on 19 November, sent after above message but translated earlier, contained instructions to listen for an abbreviated "Winds" message in general intelligence broadcasts repeated five times at beginning and end, i.e., only the word East, West, or North would be spoken five times.
A 28 Nov Circular message from Tokyo on 20 November said U.S.-Japanese situation would not "permit any further conciliation by us" and rejected all feelings of optimism.
A 22 Nov Tokyo informed Washington on 22 November that, by 29 November if agreement had not been reached, "things are automatically going to happen."
  24 Nov OPNAV message warned of possible Japanese "aggressive movement" toward Philippines, Guam, or any direction.
A 26 Nov Tokyo message to Washington on 26 November contained telephone brevity code to be used because "telegrams take too long." The code covered topics under negotiation, situations, and personalities.
  27 Nov OPNAV WAR WARNING message.
A 29 Nov Message on 26 November from Nomura to Tokyo recommended that Japan break diplomatic relations with the U.S. in a formal manner rather than "enter on scheduled operations" without prior announcement particularly since "our intention is a strict military secret." A formal break would avoid responsibility for the "rupture."
N 2 Dec A circular message from Tokyo on 27 November contained another brevity code in which codewords were assigned specific meanings, e.g., "Japan's and USA's military forces have clashed" equals, "HIZIKATA MINAMI."


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N 28 Nov A telephone conversation on 27 November between Washington (Kurusu) and a foreign office official in Tokyo named Yamamoto. Tokyo used telephone code to convey a message referring to an attack on the U.S.
  29 Nov OPNAV WAR WARNING message. Text indicated Army had also been notified.
A 1 Dec Message from Tokyo to Berlin on 30 November directed the Japanese ambassador to inform Germany that U.S. relations had ruptured and that "war may break out quicker than anyone dreams." Regarding Russia, Tokyo stated that if Russia reacted to her move southward and joined hands with England and the U.S., Japan was "ready to turn on her with all our might." Tokyo requested the Germans and Italians to maintain "absolute secrecy."
N 1 Dec Message from Tokyo to Washington discussed means of allaying U.S. suspicions regarding Japanese reactions to the U.S. proposal of 26 November. News media were to be advised that "negotiations are continuing." A plan was discussed to make a formal presentation in Washington vice Tokyo. The message queried president's reaction to Tojo's bellicose speech.
N 1 Dec A circular message from Tokyo on 1 December advised Washington that London, Hong Kong, Singapore, and Manila had been instructed to destroy code machines.
  2 Dec OPNAV instructed CINCAF to establish defensive patrols.
A 4 Dec Message from Rome to Washington on 2 December said that Tokyo believed the Hull note of 26 November "absolutely unacceptable," and "a conflict(?) in the near future is considered very probable." Rome also said Tokyo believed American Navy in Pacific was "not strong enough for decisive action."
N 3 Dec Message from Tokyo to Washington on 2 December instructed Washington to burn all codes except one copy of the codes being used in conjunction with the machine (i.e., PURPLE, the O Code, and the abbreviation code. Washington was also to burn messages, other secret papers, and telegraphic codes, and possibly to destroy one machine.
  3 Dec An OPNAV message regarding Japanese instructions to burn codes.
N 6 Dec Messages from Berlin and Rome to Tokyo on 3 December described Japanese attempts to obtain German and Italian assurances that they would follow the Japanese declaration of war on the U.S. with their own. Hitler was not available, but Mussolini agreed.


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  4 Dec OPNAV ordered U.S. codes destroyed.
N 6 Dec Washington confirmed destruction of codes on 5 December.
N 6 Dec Tokyo message on 5 December ordered four individuals in Washington to leave immediately. The translation contained a note which identified one as head of Japanese espionage in the Western Hemisphere and the others as his assistants.
A 6 Dec Tokyo message to Washington on 6 December alerted Nomura that a formal reply to the 26 November note had been prepared, was very long, and would be in 14 parts.

The messages quoted in this appendix are taken from Radio Intelligence Publication Number 87Z, "The Role of Radio Intelligence in the American-Japanese Naval War," Vol. I, Section A, by Ensign John V. Connorton, USNR. SRH-012, RG 457.

Published: Mon Jul 06 14:52:15 EDT 2015