I seriously doubt that anyone here is trying to justify Japan's aggression in the 30's and 40's. That is not what is at issue.

What is at issue is whether there was any actual need to drop A-bombs on Japan OR to launch an invasion of the Japanese mainland either. My answer to that is "No" in both cases. Truman may have seen it differently, and in fact I'm sure he saw it differently. So Truman and I would disagree on that one. Fine. We would probably disagree on any number of things.

In a war one fights to win. Winning does not necessarily require complete annihilation of, occupation of, or complete humiliation of the opponent. It just requires attaining a winning position, that's all.

Let me give a hypothetical example. The South could conceivably have won the Civil War, had they held out long enough and won certain key battles (like Gettysburg), but winning would not have required them to entirely conquer the North (which would have been beyond their capability anyway), nor would it have required them to force an unconditional surrender on the North, nor would it have required them to burn Washington or force the North to disarm its entire armed forces or any other such overweaning action.

Nope. Winning would simply have required them to convince the North that IT could not win, by inflicting serious enough defeats on the North. It was the North that was seeking unconditional surrender.

It was abundantly clear to even ordinary servicemen in Japan that Japan could not win by 1945. Totally, absolutely obvious! Everybody knew it, but hardly anyone dared to say it openly, because of their peculiar honor system. They had already lost. The government would have fallen in disgrace with or without an American invasion, and not too far down the line. The High Command would have been disgraced and kicked out. Their empire was in a shambles. Their navy was defunct. Their air force was nearly defunct. Their armies were helpless to do anything about the situation.

There is no need to do much further to a nation in such straits, and there is certainly no need to either invade them or drop A-bombs on them. Just blockade them, let their economy starve, and wait for them to ask for terms (which they in fact were already asking for...but through the Russians! Bad choice of intermediary. However, they didn't know who else to do it through, because they didn't have diplomatic contacts with anyone else at that point.)

The reason I disagree with Truman is partially because of hindsight. I fully realize that he may have thought it necessary to invade Japan or use the Bomb. That he did think so was a form of hubris common in great victorious powers.

And...he may have been in a hurry...because of the Russians. They had plans for the Japanese holdings on the Asian mainland.