In "The Making of the Atomic Bomb" by Rhodes, a poignant point was made, originating from people like Bohr, who were definitely on the peaceful side: without demonstrating the effect of the atomic bomb, the "nuclear taboo" would not have come into existence, and the first large conflict between nuclear powers would have seen a terrible outcome. The use of the bomb was inevitable, so it was sadly better to use it in a restricted war, before the US and the CCCP would use them against each other and the rest of the world.
That might have been a better argument if the USSR[0] had had the bomb in 1945[1]?
Lagniappe: https://www.youtube.com/watch?v=oRLON3ddZIw#t=15s
[0] first test: 29.08.1949
[1] a year in which the US and USSR were, however tenuously, still allied
> And to the others he said in mine hearing, Go ye after him through the city, and smite: let not your eye spare, neither have ye pity:
> Slay utterly old and young, both maids, and little children, and women...
Ezekial 9:5-6
> Now go and smite Amalek, and utterly destroy all that they have, and spare them not; but slay both man and woman, infant and suckling, ox and sheep, camel and ass.
1 Samuel 15:3
> And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark.
Genesis 7:23
Two and a half thousand years later, human nature is unchanged. How easily we make peace with wholesale slaughter.