JF Ptak Science Books Post 1868 [Part of a long series on the History of Atomic and Nuclear Weapons, here.]
The fate of failed Japan was being decided in the hands of the United States in the middle of July, 1945. The Imperial Navy and Air Force was basically finished, leaving the sea and sky open for complete domination, and the Imperial Army was still fit to fight, if not well supplied. That said, there was still the issue of possible invasion, and of fighting on a mountainous battlefield against a dedicated indigenous population that could still field millions of more fighters if not soldiers.
As Secretary of War Henry Stimson outlined in his Top Secret memo to President Truman on 2 July 1945, "Proposed Program for Japan", there was little left to fight:
Japan has no allies.
Her navy is nearly destroyed and she is vulnerable to a surface and underwater blockade which can deprive her of sufficient food and supplies for her population.
She is terribly vulnerable to our concentrated air attack upon her crowded cities, industrial and food resources
She has against her not only the Anglo-American forces but the rising forces of China and the ominous threat of Russia.
We have inexhaustible and untouched industrial resources to bring to bear against her diminishing potential.
We have great moral superiority through being the victim of her first sneak attack.
--Source: The Nuclear Files, here.
Little left, of course, save for the millions of defenders fighting on their own soil for their own soil. Which, in the end, turns out to be almost everything insofar as the use of the atomic bomb is concerned.
This is of course a very complex and long story on the decision to use the bomb, and I don't pretend to even begin such a thing here. But what I would like to just point out, that in the middle of all of the discussion, the supreme commander of the allied forces in Europe, General Dwight Eisenhower, was not in favor of using the bomb. Eisenhower was with Stimson when the Secretary of War received the coded telegram giving him the positive results of the atomic test in the Jornada del Muerto, the Trinity test, at Alamogordo, New Mexico. Eisenhower wrote of the experience:
"The cable was in code, you know the way they do it. "The lamb is born": or some damn thing like that. So then he (meaning Stimson) told me they were going to drop it on the Japanese. Well, I listened, and I didn't volunteer anything because, after all, my war was over in Europe and it wasn't up to me. But I was getting more and more depressed just thinking about it. Then he asked for my opinion, so I told him I was against it on two counts. First, the Japanese were ready to surrender and it wasn't necessary to hit them with that awful thing. Second, I hated to see our country be the first to use such a weapon. Well ... the old gentleman got furious. And I can see how he would. After all, it had been his responsibility to push for all the huge expenditure to develop the bomb, which of course he had a right to do, and was right to do. Still, it was an awful problem1."--Richard Rhodes, The Making Of The Atomic Bomb (Touchstone Books, 1986), page 688 (though not an expert in this collection of areas when he started, and not an historian of science, Rhodes has written perhaps the definitive history of the Project).
It wasn't entirely clear that the Japanese were ready to surrender at this point as Eisenhower said, not really. And it also wasn't necessarily the case that the entrance of the Soviet Union into the war in the Pacific would have resulted in an easier time in fighting on the ground. And General LeMay--who strategized that he could destroy the Japanese capacity for war from the air by bombing 30-60 cities over the June-August period--had actually carried out his plan, striking 58 cities and nearly destroying half of Tokyo, but still the Japanese fought on.
But it is interesting that after all of this time, and dozens of millions dead, that Eisenhower would be so circumspect in using the atomic bomb to finally force the hand of the Japanese in resignation.
The fact remains though that it still took several days after the dropping of the second atomic bomb on Nagasaki for the Japanese to accept what were essentially the same pre-bomb terms of surrender.
1. I should point out that Stimson's liability in the decision to build the bomb (if such a thing existed) was relieved when the bomb was tested successfully--its actual employment was beyond the judgment of his actions. (Stimson himself said that he was relieved of the responsibility of having spent "two billions of dollars" on the bomb and that he no longer would have to fear spending years in prison for a failed effort.