Piercing the Fog - Air Force Historical Studies Office

Piercing the Fog
CBI, ULTRA intercepts, done in Washington, Honolulu, India, or Brisbane,
Australia, came to play a significant role in the AAF’s planning and operations.
The specific importance of this source in the war against Japan varied greatly
from theater to theater and from numbered air force to numbered air
The American effort against Japan began in the 1920s, continuing at
various levels up to and throughout the war. Initially, its focus was unlike that
of the Allies in Europe. During the late 1930% the bulk of German message
traffic intercepted and decrypted by the British dealt with military topics, in part
because of the covert German efforts to conceal their own remilitarization
efforts which were specifically prohibited by the Versailles treaty.174 Fearing
German military efforts most, the British directed decrypting efforts toward
these areas; inasmuch as the Americans were most concerned with Japanese
economic expansionism, their priorities concentrated on this threat.’75 The bulk
of Japanese message traffic intercepted and decrypted by the Americans in the
1930s concerned Japanese naval operations and diplomatic and political matters
directly related to Japan’s expansionist foreign policy.
With respect to encrypting messages, the Japanese during the 1930s relied
on a system similar to the Germans’: machine-enciphered messages. The
Japanese systems were more formidable than those of the Third Reich, for the
Japanese language is extremely difficult for Westerners to master. To
Americans, the logic of the German language (its sentence structure and thought
progression) came relatively easily because of common cultural and linguistic
traditions. Asian conceptualization in both thought process and sentence
structure was dramatically different for all but those few Americans who had
studied and understood Asian culture. The shortage of American linguists
comfortable in the Japanese language and perceptive to Japanese culture limited
Pacific ULTRA operations from their inception during the 1930s until well into
the war.176
American code breakers during the 1930s focused their efforts on Japanese
naval and diplomatic traffic because they had been able to break those
encryptions, whereas they could not penetrate the Japanese Army’s cipher
system. The Japanese were in the process of establishing an overseas empire
and understandably had to rely upon wireless communications rather than land
lines for diplomatic discussions. Although most Americans were unfamiliar
with the internal functioning of Japanese society, Washington’s analysts felt
more comfortable with Japanese diplomatic efforts because these tended to
follow Western logic. As a consequence, American code breaking efforts
against the Japanese were better developed in a diplomatic rather than in a
military context.
There existed a limited American appreciation of Japanese military affairs
in general and air operations in particular. Most analysis of Japanese military
and aviation matters in the 1930s was secondhand. It came from Japanese
diplomatic appreciations of the military situation sent between the Tokyo
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