Interesting. Never really knew about this. However, the Japanese empire was a very, VERY proud empire with an even more proud military. I mean, even after the first bomb was dropped, they didn’t surrender. And even when the Emperor wanted to surrender, the military would have none of it and even instigated a coup to keep the war going and their honour intact. A conditional surrender may have been preferable, but Truman wanted unconditional surrender. And the bombs imho definitely ensured they would get that. Why was unconditional surrender preferable? To ensure a finality to the struggle. An armistice is no finality (Korea), a conditional surrender cannot ensure a complete cessation of hostilities in the future also (though this is debatable). An unconditional surrender with subsequent socio-political restructuring by the victor? You just got yourself peace and an ally (and perhaps more) all in one go. I think that was the endgame and justification.
