Piercing the Fog - Air Force Historical Studies Office

The Pacific and Far East
The information gained by the Japanese was very good and probably repre-
sented operational strengths, with the differences between their estimates and
the actual strengths possibly being airplanes in depot maintenance or reserve.
Little wonder in light of this information that Kenney had been concerned a year
previously when the Japanese shot down Brig. Gen. Kenneth Walker’s B-17
after a raid on Rabaul on January 5, 1943. Walker probably had limited if any
knowledge of the growing but as yet not fully developed radio-intercept
intelligence activity in the Pacific. Despite that, his capture might have had
serious consequences as even then the secrecy surrounding the subject was
rather loosely handled. Fortunately for the Allies (and unfortunately for the
general), Walker was never found, apparently having died in the ~rash.’~
Although the Japanese had disregarded the creation of strategic intelligence
organizations to the detriment of their long-term plans and operations, they
remained capable of tactical accomplishments that gave them insights into
Allied air operations. Kenney’s knowledge of his enemy’s understanding of
Allied capabilities certainly played a part, although probably minor, in his own
plan formulation.
Moreover, the Japanese were not so arrogant as to completely disregard the
dangers of Allied intelligence successes. After the March 10, 1944, sinking of
a small Japanese freighter, the Japanese sought out one of the ship’s officers and
queried him about the code books the ship carried. They then reminded all
concerned of the dangers to shipping and troops in transit should code
information fall into the wrong hands. Later in March, after the destruction of
a convoy to Wewak and the coincident loss of its cryptographic materials, the
Japanese changed their sea transport cryptographic system, reducing tempo-
rarily the Allied use of this source. They still did not realize the true ability of
the Allies to read their enciphered messages.”
Intelligence specialists at CB and Fifth Air Force headquarters lacked a
complete understanding of Japanese information, but they continued to learn of
enemy capabilities and tactics as they read his radio signals. The Allies
determined, for example, that the Japanese had ascertained from the lieutenant
who had flown the B-24 that Allied airmen changed radio frequencies and call
signs on each mission. Routine Japanese Y-Service work indicated that the Fifth
and Thirteenth Air Forces coordinated operations, and that Japanese forces
should be on the alert against large-scale operations in New Guinea and the
Solomons after mid-March 1944. The Japanese discerned the direction of Allied
intentions correctly, although they were unable to anticiRate precisely what
would happen or to deflect the Allied campaign. On March 20, Admiral
Halsey’s SOPAC units landed on Emirau Island near the major Japanese base
at Kavieng. In a March 25-27 conference in Brisbane, MacArthur, Nimitz,
Halsey, Kenney, and other senior officers discussed major upcoming operations.
On April 22, MacArthur landed his Sixth Army at Hollandia and nearby
locations. The Hollandia effort had been preceded by a major Allied Air Forces
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