Alsos Mission - Japan

Japan

Plans for the invasion of Japan incorporated an Alsos Mission. Japanese fire balloon attacks on the United States had aroused fears that the technique might be used in combination with biological agents, which the Japanese were known to be experimenting with. In March 1945, the physicist and seismologist L. Don Leet was appointed as head of the scientific section of the Alsos Mission to Japan. Leet had previously worked with the Manhattan Project on the Trinity nuclear test. Plans were drawn up to prepare and equip a T-Force along the lines of the one in Europe, but made up of personnel already in the Pacific. The mission differed from its European counterpart in that there was no Allied representation, or representation of other American intelligence agencies. Moreover, responsibility for nuclear matters was subsequently handled by a separate Manhattan Project organized by Groves.

Leet's group reached Manila in July 1945, where they met with the intelligence staff of General of the Army Douglas MacArthur's Army Forces, Pacific. Following the surrender of Japan the mission traveled to Japan and visited various research establishments including Tokyo Imperial University, Waseda University, Tokyo Institute of Technology, the Institute of Physical and Chemical Research, the Institute for Materials Research, Tokyo Shibaura Denki (Toshiba), the Japan Society for the Promotion of Science, the National Research Council, and the Board of Technology. The mission, which included Karl Compton, interviewed over 300 Japanese scientists and produced reports on Japanese research into radar, rockets, and other developments, including chemical and biological warfare. The Manhattan Project Intelligence Group, under the command of Philip Morrison, arrived in Japan in September 1945 and examined Japan's wartime nuclear weapons program. The group concluded that lack of uranium ore and low priority had doomed the Japanese effort. However, they reported that contrary to the popular belief, Japan's nuclear physicists were every bit as good as those of other nations.