On August 11th, 1945, two days after the bombing of Nagasaki, a message
was dispatched from Major General Leslie R. Groves to Brigadier General
Thomas F. Farrell, who was his deputy in atomic bomb work and was
representing him in operations in the Pacific, directing him to
organize a special Manhattan Project Atomic Bomb Investigating Group.
This Group was to secure scientific, technical and medical intelligence
in the atomic bomb field from within Japan as soon as possible after
the cessation of hostilities. The mission was to consist of three
groups:
1. Group for Hiroshima.
2. Group for Nagasaki.
3. Group to secure information concerning general Japanese activities in
the field of atomic bombs.
The first two groups were organized to accompany the first American
troops into Hiroshima and Nagasaki.
The primary purposes of the mission were as follows, in order of
importance:
1. To make certain that no unusual hazards were present in the bombed
cities.
2. To secure all possible information concerning the effects of the
bombs, both usual and unusual, and particularly with regard to
radioactive effects, if any, on the targets or elsewhere.
General Groves further stated that all available specialist personnel
and instruments would be sent from the United States, and that the
Supreme Allied Commander in the Pacific would be informed about the
organization of the mission.
On the same day, 11 August, the special personnel who formed the part
of the investigating group to be sent from the United States were
selected and ordered to California with instructions to proceed
overseas at once to accomplish the purposes set forth in the message to
General Farrell. The main party departed from Hamilton Field,
California on the morning of 13 August and arrived in the Marianas on
15 August.
On 12 August the Chief of Staff sent the Theater Commander the
following message:
"FOR MACARTHUR, SIGNED MARSHALL:
"GROVES HAS ORDERED FARRELL AT TINIAN TO ORGANIZE A SCIENTIFIC GROUP OF
THREE SECTIONS FOR POTENTIAL USE IN JAPAN IF SUCH USE SHOULD BE
DESIRED. THE FIRST GROUP IS FOR HIROSHIMA, THE SECOND FOR NAGASAKI,
AND THE THIRD FOR THE PURPOSE OF SECURING INFORMATION CONCERNING
GENERAL JAPANESE ACTIVITIES IN THE FIELD OF ATOMIC WEAPONS. THE GROUPS
FOR HIROSHIMA AND NAGASAKI SHOULD ENTER THOSE CITIES WITH THE FIRST
AMERICAN TROOPS IN ORDER THAT THESE TROOPS SHALL NOT BE SUBJECTED TO
ANY POSSIBLE TOXIC EFFECTS ALTHOUGH WE HAVE NO REASON TO BELIEVE THAT
ANY SUCH EFFECTS ACTUALLY EXIST. FARRELL AND HIS ORGANIZATION HAVE ALL
AVAILABLE INFORMATION ON THIS SUBJECT."
General Farrell arrived in Yokohama on 30 August, with the Commanding
General of the 8th Army; Colonel Warren, who was Chief of the
Radiological Division of the District, arrived on 7 September. The
main body of the investigating group followed later. Preliminary
inspections of Hiroshima and Nagasaki were made on 8-9 and 13-14
September, respectively. Members of the press had been enabled to
precede General Farrell to Hiroshima.
The special groups spent 16 days in Nagasaki and 4 days in Hiroshima,
during which time they collected as much information as was possible
under their directives which called for a prompt report. After General
Farrell returned to the U.S. to make his preliminary report, the groups
were headed by Brigadier General J. B. Newman, Jr. More extensive
surveys have been made since that time by other agencies who had more
time and personnel available for the purpose, and much of their
additional data has thrown further light on the effects of the
bombings. This data has been duly considered in the making of this
report.