THE SILENT WAR AGAINST THE JAPANESE NAVY

by

Capt. Duane L. Whitlock,
U.S. Navy (Ret'd)

ON THE DAY THE BOMBS FELL on Pearl Harbor, the U.S. Navy, or at least a tiny segment of it, had had the Imperial Japanese Navy under attack for about twenty years. The attack was, of course, a silent one, of which the Japanese were totally unaware. It began in 1921, when the Office of Naval Intelligence (ONI) surreptitiously acquired a photographic copy of the "Imperial Japanese Navy Secret Operating Code-1918." [1] The code was in essence a dictionary containing a hundred thousand entries, and it took five years to translate; only two Japanese linguists were available, and there was no particular urgency or incentive attaching to the project. After all, having a code book is of no great advantage if one does not have access to messages being encrypted in that code.

ONI at the time did not have that access, and gaining it was not a simple matter, because the Japanese use a different telegraphic code for radio communications than does the rest of the world. Keyed to the Japanese alphabet, or syllabary, known as Kata Kana, it contains nearly twice as many dot-and-dash combinations as the Morse code. Kata Kana, sometimes referred to as "hen tracks," is a simple pictorial means of phoneticizing the Japanese spoken language. In 1923, the Chief of Naval Operations (CNO), perhaps unaware of the nature of the Japanese telegraphic code, requested that Asiatic and Pacific fleet radio operators listen in their spare time for enciphered foreign radio messages. [2] To what extent this invitation served its purpose is unknown, but several Navy and Marine Corps operators in the Far East did teach themselves to recognize and intercept Japanese radio communications. One of these operators, Chief Radioman Harry Kidder, was serving in the Philippines. With the help of the Japanese wife of a shipmate, he learned the Kata Kana syllabary, taught himself the telegraphic equivalents of all the Kata Kana characters, and began to intercept Japanese messages. [3] Whether anyone in Washington was aware of his accomplishment at the time is not clear; that it paid enormous dividends in years to follow is an indisputable matter of record.

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