Pearl Harbor: Who Blundered?

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Japan would acquiesce to our government’s demands that she withdraw from Indochina only upon “establishment of an equitable peace in the Pacific area” and, further, upon “supply to Japan [by the U.S. of] a required quantity of oil.”

In 1940, our cipher experts had cracked the Japanese secret codes—a cryptoanalytical procedure known in the War Department as “Magic.” Hence our government knew that the envoys had received instructions to press for American acceptance of this “final proposal” by November 25. The ambassadors had been warned that for reasons “beyond your ability to guess” this was essential, but that if the “signing can be completed by the 29th” the Imperial Japanese government would wait. “After that things are automatically going to happen.”

It was also known through Magic radio intercepts that a large proportion of Japanese military strength—land, sea, and air—was concentrating in the Indochina and South China Sea areas. No evidence of aircraft carriers had been found, however, either in those areas or in the Japanese mandated islands. Intelligence agencies, monitoring Japanese radio traffic, considered it probable that the carriers were still in their home waters, but they were not certain.

On this basis Marshall, Stark, and their respective staffs concluded that the Japanese were preparing to strike in Southeast Asia; this threat, of course, included the Philippine Commonwealth. Accordingly our Army and Navy commanders in the Philippines and at Guam had been specifically warned. The commanders in Hawaii, Panama, Alaska, and on the West Coast were kept informed of important developments.

This was the situation as Marshall and Stark saw it early on November 25. From that time on events succeeded one another with increasing rapidity, both in Washington and in Hawaii. This is how they unfolded:

Washington, Tuesday, November 25

Marshall and Stark attended a “War Council” meeting with the President, Secretary of State Cordell Hull, Secretary of War Henry L. Stimson, and Secretary of the Navy Frank Knox. Were the Japanese bluffing? Hull thought not; rejection of their terms would mean war. “These fellows mean to fight,” he told the group. “You [Marshall and Stark] will have to be prepared.”

Adequate preparation could not be guaranteed by either service chief. The great draft army was still only a partly disciplined mass. The Navy, better prepared for an immediate fight, was still far from ready for an extended period of combat. Marshall urged diplomatic delay. If the State Department could hold war off for even three months, the time gained would be precious, especially in the Philippines, where Douglas MacArthur’s newly raised Commonwealth Army was only partly organized and equipped.

Perhaps the State Department’s formula— modus vivendi they called it—which had been sent by cable to our British, Chinese, Australian, and Dutch allies for comment—would gain the needed time. This was a proposal for a three-month truce in Sino-Japanese hostilities, during which the United States, in return for Japan’s withdrawal from southern Indochina, would make limited economic concessions to her.

It was evident to all concerned that otherwise hostilities were almost certain to break out within a few days. The President, noting Japan’s proclivity for attacking without a declaration of war, impressed on all concerned that if war came, it must result from an initial blow by Japan. How, then, asked Roosevelt, could the United States permit this without too much danger to itself?*

That evening Stark wrote a lengthy warning to Kimmel in Hawaii, informing him that neither the President nor the Secretary of State “would be surprised over a Japanese surprise attack,” adding that while “an attack upon the Philippines would be the most embarrassing thing that could happen to us…I still rather look for an advance into Thailand, Indochina, Burma Road areas as the most likely.” Marshall reviewed the incoming and outgoing messages to overseas commanders, and busied himself with the almost numberless duties of his most important task: preparing our Army for combat.

Honolulu, Tuesday, November 25

Kimmel and Short had more than a passing interest in the status of our negotiations with Japan. Admiral Kimmel had been kept informed of the increasingly strained relations by frequent frank and newsy letters from Admiral Stark. One of these, dated November 7, had said in part: “Things seem to be moving steadily towards a crisis in the Pacific.…A month may see, literally, most anything…It doesn’t look good.”

Admiral Kimmel undoubtedly was thinking of that letter when he reread the official radio message which he had received the day before, November 24: