It was impossible to announce the bombing of Hiroshima to the American people without giving particulars, including the several-year history of the bomb project. It was also impossible to release such an explanation without crediting it to the president of the United States. Officials of the war department hence put together a detailed commentary in the form of a press release, which the president agreed to while at Potsdam; Secretary of War Stimson was present during the Potsdam Conference's first days and discussed the press release with him at that time.

After returning to Washington, Stimson revised the draft of the release in light of the Potsdam Declaration, the dramatic results of the Alamogordo test of a plutonium device, and a few minor suggestions by the British government. On July 30 the secretary sent a radio message to Truman at Babelsberg asking permission to use the release at any time beginning Wednesday, August 1. He added that he was sending a courier with the text on Tuesday, July 31.

Here, in the proposal that the president "sign off" on the press release, lay a fascinating situation. The go-ahead for using atomic bombs had been given in the letter of July 25 from General Thomas T. Handy to General Carl Spaatz (document 6). This was a service document; no copy of a presidential authorization has ever appeared. Truman, of course, could have canceled the Handy letter at any time short of use of the bomb. In effect, therefore, the presidential sign-off for the press release was a confirmation of the Handy letter. Upon receiving Stimson's radio of July 30 the president wrote an undated chit in longhand:

SecWar Reply to your 41011 suggestions approved. Release when ready but not sooner than August 2. HST

Full Cable, from Secretary of War to President Truman, July 30, 1945, with a handwritten response by the President on the reverse (2 pages).

The text of the above was radioed to Washington. Truman desired to wait until August 2 because he was to leave Potsdam that day and fly to England. There he would board the heavy cruiser U.S.S. Augusta, and be, on the high seas, away from Potsdam, when the Hiroshima bomb was dropped. He had told Stalin about the bomb only in general terms, not describing it as atomic.

One point about the following document: The force of the bomb, estimated at 20,000 tons of TNT, was really an estimate of the force of the test device. The Hiroshima bomb, a uranium, or fission, bomb (dubbed "Little Boy" because of its tubular shape) was the only nuclear weapon available that employed U-235. Both the test device and the bomb (called "Fat Man") dropped on August 9 on Nagasaki, three days after Hiroshima, used plutonium and had rounded shapes and a different firing mechanism. The Hiroshima bomb, one of a kind, was of unreckoned power; it was not possible until years later, after many measurements of the collapsed buildings, to define its force as equal to 13,000 tons of TNT.

Document:August 6, 1945 Draft of a Public Statement. View the document

Notes:

1. In Berlin in 1938 three German scientists demonstrated that it was possible to split the uranium atom and thereby showed that a nuclearbased explosion was feasible. In the early part of World War II the fear was great that the German scientists, ahead of British and U.S. scientists in their discovery of 1938, might construct a bomb. Fear of such a possibility existed until after the Allied invasion in 1944; and when British and American troops reached the Rhine, some months later, one of the first happenings was the appearance of scientists in the company of the troops, who then took samples of the Rhine's water to see if it contained traces of uranium. There were no traces; German physicists had failed to construct a bomb or come anywhere near doing so. The well-known German V-is were drone planes released from continental launching pads that flew over Britain and dropped their explosive cargoes. They were easily shot down and did little damage. Much more destructive, and impossible to intercept, were the ballistic V-2s that carried devastation, including the breaking of windows throughout London; the V-2s harried London's defenders until capture of their launching sites in the autumn and winter of 1944-1945.

2. At the beginning of the war, scientists in the Manhattan Project decided to go two ways in the production of fissionable material. Because of the need for enormous amounts of electrical power they constructed plants at Oak Ridge, Tennessee, and at Hanford in Washington state. The Oak Ridge plant produced U-235, the lighter fissionable isotope of uranium, by pumping U-238 in gaseous form through a long series of sieves; the heavier isotope remained behind. At Hanford the scientists employed reactors to produce plutonium from uranium.

3. The president naturally did not say that the United States at that time possessed only one other nuclear weapon: the plutonium bomb that would be dropped on Nagasaki. A second plutonium bomb would not be ready for several weeks.

4. The installation near Santa Fe was the Los Alamos Scientific Laboratory under direction of I. Robert Oppenheimer.

5. Results of the experiment in Berlin in 1938 were announced immediately, in accord with usual practice of scientists, which was to publish at once. When the Anglo-American bomb project began, three years later, its discoveries of course remained secret.

6. The president eventually recommended establishment of an Atomic Energy Commission (ABC), which took over from the wartime Manhattan Project on January 1, 1947. Meanwhile discussions within the administration led to the Acheson-Lilienthal plan, named for Undersecretary of State Dean Acheson and for the then chairman of the Tennessee Valley Authority, David F. Lilienthal, who became the first chairman of the ABC. With minor changes the plan of Acheson and Lilienthal became the Baruch plan, named for the president's special envoy to the United Nations Organization, Bernard M. Baruch, who offered the plan to the UN-where it failed to gain acceptance.