Yes, I think he was right and I believe I would have done the same. Millions more lives were at stake. Granted the US would have won the war either way with Japan, but a what cost? If we hadn't had military strength afterward the world would be very different now.

Invading Japan would have been extremely costly in lives. It is a big place and would not have surrendered quickly or easily. But that pales in comparison to the importance of the first hand knowledge the world now has of the horror of nuclear war. Had we not exploded those bombs and then witnessed the horrific aftermath, our knowledge of what might happen would have been hypothetical. I'm sorry the Japanese had to suffer, they're good people, but their sacrifice may have averted total nuclear annihilation for the whole human race. So perhaps unlike most suffering, this time it had purpose and meaning.

Yes, especially in light of plans we were not entirely aware of (though we had some inkling of them before) for how the Japanese military intended to combat any invasion. Basically use the civilian population as a human wave, send them at the beachheads first with literally little more than sharpened sticks for improvised spears (with of course a few soldiers behind to ensure they face the right way). Even though there was almost no chance they would get close enough to use their 'spears', that was the intent. Every civilian like that which caught a bullet would mean one less round the invaders had to fire against the actual soldiers who would also resist to the bitter end (Iwo Jima and Okinawa particularly come to mind, but also Tarawa, Saipan, and others are good examples of the fanatical resistance of Japanese soldiers). Even conservative estimates were over one million Allied casualties, which was the reason we wanted Britain, the USSR, and everyone else in on it; to spread the losses out some. It would have easily been in the millions (perhaps tens of millions when it was all said and done) on the Japanese side. Awful though dropping the bombs was I think it was the lesser of the evils Truman was faced with. The first one (Hiroshima, IIRC) got their attention and the second served to make the Emperor realize that unless he overrode the desires of Tojo and others to resist to the end then his empire would be little more than ashes. Not dropping the bombs would have made no difference as far as the future nuclear arms race was concerned, it had already been researched extensively by Germany and others and it would have been perhaps a few more years before someone else figured it out. It is also likely that without that first experience of the real horror of it, someone would have used them on a larger scale (perhaps the Cold War would have turned hot).

Yep, calmed their asses down and they have not acted up since them.

Yes he was justified. They brought it to us when the attacked all over the Pacific, had been treating the Chinese with horror for years. Shouted with glee when they watched the beheading of out air crews. It was a horrible death to so many, but that is war, and seems to continue to this day somewhere on this planet.