Piercing the Fog - Air Force Historical Studies Office

The Pacific and Far East
18, the pilots took off, flying northward at extremely low altitude and carrying
external fuel tanks on their planes to give them the needed range.52
By 9:34 AM, sixteen P-38 Lightning fighters intercepted two Japanese
Mitsubishi Betty bombers and six Zero fighters over Bougainville Island. In the
ensuing swirl of aerial fighting, the Americans destroyed both bombers. Killed
in the first bomber as it crashed into Bougainville’s jungles was Admiral
Yamamoto. The successful ambush of Yamamoto later became one of the most
highly publicized incidents of the Pacific war. This action also endangered
America’s ability to read Japan’s encrypted message traffic. Virtually everyone
involved in the killing of Yamamoto, including the P-38’s ground crews, came
to know the source of the information. The British were aghast that American
policy permitted such a risk. As it was, officials at BP withheld full disclosure
of their operation for several months. Had the story reached Japan from any
source, and had the Japanese realized its significance, they could have altered
their radio transmission practices and foreclosed an extremely valuable Allied
insight into their planning. Fortunately, the Japanese failed to understand the
true nature of the attack. Ambushes such as the one that killed Yamamato were
unusual events, not central to the war effort. Over time, a more methodical use
of technical information came to expand on the reports obtained from ULTRA.
Electronic intelligence gathering efforts began in the Pacific war only after
the capture of some Japanese equipment in August 1942 at Guadalcanal. A
badly damaged Mark 1 Model 1 radar set found at Henderson Field was quickly
packed and sent to the Naval Research Laboratory at Anacostia, in Washington,
D.C. Soon, the Navy sent a team with airborne radar intercept equipment to the
SOPAC. This team made the first ferret flight in search of Japanese installations
in the region, flying an AAF B-17 from Espiritu Santo to Guadalcanal,
Bougainville, and returning on October 31, 1942. Other flights in November
carried Allied crews but found no enemy radar signals. Since the teams
collected no evidence of Japanese radar, operational interest in the Pacific
temporarily waned. Development of more effective electronic search aircraft
continued in the United States, and they subsequently deployed to North Africa.
At about the same time that the airborne searches were underway in the
Solomons, a Navy submarine carrying similar radio-receiving equipment picked
up radar signals while on patrol off Japan. The earlier absence of radar reception
by the airborne teams resulted in much uncertainty over whether the Japanese
in the area lacked extensive radar equipment or if the early detection sets simply
would not pick up the signals. The ferret aircraft, generally B-24s or Catalina
flying boats, carried radar frequency analyzers plus equipment to determine the
relative bearing of the radar set and to measure its pulse width and pulse
repetition frequency. Not until late 1943 did the subject receive much attention
in SPA and SWPA. Then, seeing the potential importance of mapping enemy
radar as a way to avoid AA gun defenses, G-2 SWPA formed its Section 22 to
control and coordinate all Allied airborne radar and radio intelligence gathering
27 1