While MAGIC was silent on the subject of Pearl Harbor, messages in J-19 betrayed an abnormal interest on the part of the Japanese consulate in Honolulu in both Pearl Harbor and the movements of the Pacific Fleet. But MAGIC had a higher priority than J-19 traffic. American decrypters devoted most of their efforts to MAGIC, and it often took up to two weeks for a J-19 dispatch to be read, translated and distributed. On Sept. 24, 1941, the Japanese consulate was instructed to divide Pearl Harbor into five alphabetically coded zones and to report the exact positions of the Pacific Fleet as the ships lay at anchor. Incredibly, no special importance was attached to this message in Washington, and it was not passed on to the commanders in Hawaii.
"I am sure that had we seen messages that had to do with Pearl Harbor, then there would have been a different evaluation of these items of intelligence," Layton, the Pacific Fleet intelligence officer, later declared. "In the late autumn of 1941, Washington was too involved with the shipping war in the Atlantic to take proper notice of intelligence related to the Pacific. Had MAGIC decrypts been available to us, they would have at least alerted us to the possibility of an attack on Pearl Harbor."
Having failed to provide Kimmel and Short with access to MAGIC, Washington was at fault for not keeping them informed of changing conditions. With war in the Pacific imminent, high-level Army and Navy officers also blundered by not making certain that the military commanders in Hawaii were on the alert. Sound military doctrine holds that a field commander should be given all pertinent information upon which to base his decision. Failing that, he should be given explicit orders. Kimmel and Short received neither.
The misuse of MAGIC lay at the heart of the Pearl Harbor disaster. There was no clearinghouse where all the raw information on Japanese intentions could be assembled, analyzed and assessed in totality.
All the individuals cleared for MAGIC had to be their own intelligence officers and make their own analyses and interpretations of the raw intelligence -- a process in which they had little or no experience. Each message represented only a single frame in a lengthy motion picture, and they never saw the entire film. Only rarely was information from one source weighed against material from another.
Had there been a sophisticated, centralized system for evaluating all the intelligence pouring in upon Roosevelt and his inner circle, the danger signals might have been separated from the surrounding noise.
William Friedman, the man who broke the Purple code, later declared that Pearl Harbor occurred because "there was nobody in either the Army or the Navy intelligence staffs in Washington whose most important, if not sole, duty was to study the whole story which the MAGIC messages were unfolding. There was no nobody whose responsibility it was to put the pieces of jigsaw puzzle together."
Nathan Miller is the author of "The Naval Air War: 1939-1945." This is another of an occaisional series of articles about World War II.