A month before the test explosion of the atomic bomb the service Secretaries and the Joint Chiefs of Staff had laid their detailed plans for the defeat of Japan before me for approval. . . .
The Army plan envisaged an amphibious landing in the fall of 1945 on the island of Kyushu, the southernmost of the Japanese home islands. This would be accomplished by our Sixth Army, under the command of General Walter Krueger. The first landing would then be followed approximately four months later by a second great invasion, which would be carried out by our Eighth and Tenth Armies, followed by the First Army transferred from Europe, all of which would go ashore in the Kanto plains area near Tokyo. In all, it had been estimated that it would require until the late fall of 1946 to bring Japan to her knees.
This was a formidable conception, and all of us realized fully that the fighting would be fierce and the losses heavy. But it was hoped that some of Japan's forces would continue to be preoccupied in China and others would be prevented from reinforcing the home islands if Russia were to enter the war.
There was, of course, always the possibility that the Japanese might choose to surrender sooner. Our air and fleet units had begun to inflict heavy damage on industrial and urban sites in Japan proper. Except in China, the armies of the Mikado had been pushed back everywhere in relentless successions of defeats.
Acting Secretary of State Grew had spoken to me in late May about issuing a proclamation that would urge the Japanese to surrender but would assure them that we would permit the emperor to remain as head of the state. Grew backed this with arguments taken from his ten years' experience as our Ambassador in Japan, and I told him that I had already given thought to this matter myself and that it seemed to me a sound idea. Grew had a draft of a proclamation with him, and I instructed him to send it by the customary channels to the Joint Chiefs and the State-War-Navy Coordinating Committee in order that we might get the opinions of all concerned before I made my decision.
On June 18 Grew reported that the proposal had met with the approval of his Cabinet colleagues and of the Joint Chiefs. The military leaders also discussed the subject with me when they reported the same day. Grew, however, favored issuing the proclamation at once, to coincide with the closing of the campaign on Okinawa, while the service chiefs were of the opinion that we should wait until we were ready to follow a Japanese refusal with the actual assault of our invasion forces.
It was my decision then that the proclamation to Japan should be issued from the forthcoming conference at Potsdam. This, I believed, would clearly demonstrate to Japan and to the world that the Allies were united in their purpose. By that time, also, we might know more about two matters of significance for our future effort: the participation of the Soviet Union and the atomic bomb. We knew that the bomb would receive its first test in mid-July. If the test of the bomb was successful, I wanted to afford Japan a clear chance to end the fighting before we made use of this newly gained power. If the test should fail, then it would be even more important to us to bring about a surrender before we had to make a physical conquest of Japan. General Marshall told me that it might cost half a million American lives to force the enemy's surrender on his home grounds.
But the test was now successful. . . .
[At Secretary of War Henry L. Stimson's suggestion, shortly after becoming president in April 1945 Truman had] set up a committee of top men and had asked them to study with great care the implications the new weapon might have for us.
Secretary Stimson headed this group as chairman, and the other members were George L. Harrison, president of the New York Life Insurance Company, who was then serving as a special assistant to the Secretary of War; James F. Byrnes, as my personal representative; Ralph A. Bard, Under Secretary of the Navy; Assistant Secretary William L. Clayton for the State Department; and three of our most renowned scientists—Dr. Vannevar Bush, president of the Carnegie Institution of Washington and Director of the Office of Scientific Research and Development; Dr. Karl T. Compton, president of the Massachusetts Institute of Technology and Chief of Field Service in the Office of Scientific Research and Development; and Dr. James B. Conant, president of Harvard University and chairman of the National Defense Research Committee.
This committee was assisted by a group of scientists, of whom those most prominently connected with the development of the atomic bomb were Dr. Oppenheimer, Dr. Arthur H. Compton, Dr. E. O. Lawrence, and the Italian-born Dr. Enrico Fermi. The conclusions reached by these men, both in the advisory committee of scientists and in the larger committee, were brought to me by Secretary Stimson on June 1.
It was their recommendation that the bomb be used against the enemy as soon as it could be done. They recommended further that it should be used without specific warning and against a target that would clearly show its devastating strength. I had realized, of course, that an atomic bomb explosion would inflict damage and casualties beyond imagination. On the other hand, the scientific advisers of the committee reported, "We can see no acceptable alternative to direct military use." It was their conclusion that no technical demonstration such as they might propose, such as over a deserted island, would be likely to bring the war to an end. It had to be used against an enemy target.
The final decision of where and when to use the atomic bomb was up to me. Let there be no mistake about it. I regarded the bomb as a military weapon and never had any doubt that it should be used. The top military advisers to the President recommended its use, and when I talked to Churchill he unhesitatingly told me that he favored the use of the atomic bomb if it might aid to end the war.
In deciding to use this bomb I wanted to make sure that it would be used as a weapon of war in the manner prescribed by the laws of war. That meant that I wanted it dropped on a military target. I had told Stimson that the bomb should be dropped as nearly as possibly upon a war production center of prime military importance.
Stimson's staff had prepared a list of cities in Japan that might serve as targets. Kyoto, though favored by [Head of the Army Air Force] General Arnold as a center of military activity, was eliminated when Secretary Stimson pointed out that it was a cultural and religious shrine of the Japanese.
Four cities were finally recommended as targets: Hiroshima, Kokura, Niigata, and Nagasaki. They were listed in that order as targets for the first attack. The order of selection was in accordance with the military importance of these cities, but allowance would be given for weather conditions at the time of the bombing. . . .
On July 28 Radio Tokyo announced that the Japanese government would continue to fight. There was no formal reply to the joint ultimatum of the United States, the United Kingdom, and China. There was no alternative now. The bomb was scheduled to be dropped after August 3 unless Japan surrendered before that day.
On August 6, the fourth day of the journey home from Potsdam, came the historic news that shook the world. . . . Shortly afterward I called a press conference. . . . My statements on the atomic bomb . . . read in part. . . .
"We are now prepared to obliterate more rapidly and completely every productive enterprise the Japanese have above ground in any city. We shall destroy their docks, their factories, and their communications. Let there be no mistake; we shall completely destroy Japan's power to make war.
"It was to spare the Japanese people from utter destruction that the ultimatum of July 26 was issued at Potsdam. Their leaders promptly rejected that ultimatum. If they do not now accept our terms, they may expect a rain of ruin from the air, the like of which has never been seen on this earth." . . .
Still no surrender offer came. An order was issued to General Spaatz [commander of U.S. air forces in Asia] to continue operations as planned unless otherwise instructed. . . .
On August 9 the second atom bomb was dropped, this time on Nagasaki. We gave the Japanese three days in which to make up their minds to surrender, and the bombing would have been held off another two days had weather permitted. During those days we indicated that we meant business. On August 7 the 20th Air Force sent out a bomber force of some one hundred and thirty B-29s, and on the eighth it reported four hundred and twenty B-29s in day and night attacks. The choice of targets for the second atom bomb was first Kokura, with Nagasaki second. The third city on the list, Niigata, had been ruled out as too distant. By the time Kokura was reached the weather had closed in, and after three runs over the spot without a glimpse of the target, with gas running short, a try was made for the second choice, Nagasaki. There, too, the weather had closed in, but an opening in the clouds gave the bombardier his chance, and Nagasaki was successfully bombed.
This second demonstration of the power of the atomic bomb apparently threw Tokyo into a panic, for the next morning brought the first indication that the Japanese Empire was ready to surrender.
Harry S Truman, Memoirs: Year of Decisions (Garden City, NY: Doubleday, 1955), 416–426. Reprinted courtesy Ms. Margaret Truman Daniel. .