Chapter 3. The Hunt for the Winds Execute Message, 28 November – 7 December 1941

As soon as both translations of the instructions that set up the two Winds Execute messages were available to Army and Navy cryptologists and intelligence officers, they went about tasking monitoring stations to search and intercept them. The search for these messages, more precisely the appearance of the code phrases and words within either a voice or Manual morse Japanese news broadcast, was conducted against a background of increasing diplomatic and political tension between the United States and Japan. While at the time it might have been presumptive to predict the certain outbreak of war between the two nations, in the last weeks of November and into December 1941, translations of Purple traffic between Tokyo and its two negotiators, Saburo Kurusu and Kichisaburo Nomura, indicated that the current impasse might be coming to a head.

On 26 November a liaison conference of Japanese military and civilian leaders had met and decided not to use an American proposal as a basis for negotiations. Moderates, though, won another day of delay to see what Ambassador Nomura could gain in a meeting with President Roosevelt and Secretary of State Cordell Hull. But the meeting on 27 November failed to achieve any agreement. The United States still suspected Japan's intentions based on its continued adherence to the Tripartite Pact signed with Nazi Germany and Italy.^[] The growing Japanese troop strength in French Indochina could not be accepted as "defensive." In a message of 28 November (and translated by the Americans the same day), Tokyo informed its two representatives that the "negotiations will be de facto ruptured. This is inevitable." The message also instructed the two emissaries not to "give the impression" that negotiations will be broken off. Rather, they should simply say that they were awaiting further guidance from Tokyo.^[] Four days later, on 1 December, Tokyo cabled the two diplomats in Washington and told them "The date set in my message #812 (November 29th for the absolute deadline to complete negotiations) [my italics] has come and gone, and the situation continues to be increasingly critical."^[]

That same day, President Roosevelt met with his War Council, Secretaries Hull, Knox, and Stimson, Chief of Staff General George Marshall, and Chief of Naval Operations Admiral Harold Stark. At this meeting, Hull stated that there seemed to be no chance of an agreement with Japan and that a "surprise attack" [not specified] might be part of the Japanese plan. The council was aware of Japanese troop convoys sailing south, but the administration could not decide on a specific action. Still, not all in the administration believed the clock was running out. The Joint Board, a consultative body composed of the Chief of Staff and the Chief of Naval Operations and their division chiefs, had written that time might still exist to build up defenses in the Philippines, which might ultimately deter Japanese aggression to the south. Some members of the State Department suggested that Japan would hold off until the next year to attack.^[]

It was into this roiling cauldron that the translations of the two Winds instructional messages arrived. With the just published translations of the Gaimusho's instructions to its diplomats for the Winds Execute code phrases and words, the Americans believed they held at least one key that might tip off when the Japanese might initiate hostilities. The next step was to organize and stage a monitoring effort to intercept the Winds execute message. But in the next ten days leading up to the surprise attack on Pearl Harbor, American cryptologists would find that the Japanese sent out additional instructions that weaved a more complicated warning system. Inevitably, there were errors in identifying Winds Execute messages, while precious cryptologic resources, especially radio intercept operators, radio receivers, and linguists, were tied up collecting and processing plaintext broadcasts that might contain the coded Winds phrases or words.