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