The U.S. Army's acting duet of staff - General Marshall was attending the Potsdam Conference - sent out a fateful instruction to General Carl Spaatz, commander of the U.S. Army Strategic Air Forces, on July 25, the same date that the president in Babelsberg wrote of the new nuclear weapon. General of the Army Douglas MacArthur was in command of the Pacfic theater, except for naval forces and Marines under Fleet Admiral Chester W. Nimitz. The latter forces had been moving east from Pearl Harbor while MacArthur's traveled north from Australia; both were converging on the Japanese home islands.

The invasion of Japan, the first phase of which was to take place on Kyushu, was to be under MacArthur. The odd name, 509 Composite Group, indicated a group containing B-29 bombers mod fled to carry nuclear weapons. The planes had large under-the-belly hatches through which the heavy bombs had to be lifted from underground walk-in holding areas. The bombers also had to be structurally strengthened to hold the bombs' parachutes, timers, and other paraphernalia.

July 25, 1945
To:General Carl Spaatz
Commanding General
United States Army Strategic Air Forces

1.The 509 Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Nugata and Nagasaki. To carry military and civilian scientific personnel from the War Department to observe and record the effects of the explosion of the bomb, additional aircraft will accompany the airplane carrying the bomb. The observing planes will stay several miles distant from the point of impact of the bomb.

2.Additional bombs will be delivered on the above targets as soon as made ready by the project staff. Further instructions will be issued concerning targets other than those listed above.

3.Dissemination of any and all information concerning the use of the weapon against Japan is reserved to the Secretary of War and the President of the United States. No communiques on the subject or releases of information will be issued by Commanders in the field without specific prior authority. Any news stories will be sent to the War Department for special clearance.

4.The foregoing directive is issued to you by direction and with the approval of the Secretary of War and of the Chief of Staff, USA. It is desired that you personally deliver one copy of this directive to General MacArthur and one copy to Admiral Nimitz for their information.

THOS. T. HANDY] General, G.S.C.
Acting Chief of Staff

Source: Robert J. Maddox, "The Biggest Decision: Why We Had to Drop the Atomic Bomb," American Heritage, vol.46 (May-June 1995), no.3, 70.