for the bombing of Hiroshima and Nagasaki, why that reason has not entered into the official explanations for its use.
Have you ever seen that used as an official explanation, or is that explanation based on the analysis of historians?
Secretary of War, Henry Stimson, wrote the official defense of the decision (and the one that is most often quoted) in Harper's magazine in 1947:
http://www.aasianst.org/EAA/StimsonHarpers.pdf He doesn't mention the fear of a USSR invasion as the reason. James Carroll summarized the article. Quoting Stimson:
This deliberate, premeditated destruction was our least abhorrent choice. The destruction of Hiroshima and Nagasaki put an end to the Japanese war. It stopped the fire raids, and the strangling blockade; it ended the ghastly specter of a clash of great land armies.
Carroll goes on:
Stimson, like Truman before and Churchill after him, knew the importance of publicizing the costs of that alternative -- for public relations reasons, not to wrestle with the morality of it. A detailed accounting of what the invasion would entail first appeared here: five million U.S. soldiers, combat lasting well into 1946, more than a million American casualties.
But Carroll goes into great detail to show that the war could have been ended peacefully -- and well before the bomb was dropped. If fear of a Soviet invasion of mainland Japan was so great, and if that was the reason for the use of the bomb, then why didn't we use diplomatic means to end the war sooner? As Carroll explains:
Stimson's account is more nuanced in his memoir ... In that book, Stimson emphasizes the Japanese objective with their various spring and summer "peace feelers"... Stimson, by his own account and that of others, was one of those who wanted to adjust this demand (unconditional surrender) in ways that might induce a Japanese surrender...
The primary concern in Tokyo... was the fate of the Emperor. To the Japanese he was a divine being, and it was unthinkable that he be harmed or humiliated... Japanese diplomats wanted an assurance that the Emperor's status would be respected. On July 13, for example, the Americans read in a cable that Japanese Foreign Minister Shigenori Togo sent to his ambassador in Moscow, who was urgently seeking an end to the war: "Unconditional surrender is the only obstacle to peace."...
Stimson had proposed to General Marshall an abandonment of the term "unconditional surrender" as defining the war's aim... Another who favored stepping back from unconditional surrender was Winston Churchill...
Truman acted under the express influence of his new secretary of state, James F. Byrnes. The redrafted ultimatum included a sentence Byrnes composed... "There must be eliminated for all time the authority and influence of those who have deceived and misled the people of Japan".
And the tragedy of the refusal to abandon the concept of "unconditional surrender" is that we never achieved that goal anyhow, even after two atomic bombs. Carroll continues:
Not even the two atomic bombs brought about the unconditional surrender of Japan... Washington received a Morse code message from the Japanese leadership body, the Imperial Conference. "The Japanese Government," it said, "is ready to accept the terms enumerated in the joint declaration which was issued at Potsdam with the understanding that said declaration does not compromise any demand which prejudices the prerogatives of His Majesty as a sovereign ruler."
The Americans accepted that, and the war was over. But there seems to be little reason why the same couldn't have been accomplished several days or weeks earlier, without use of the two bombs.