Off-topic, but of course there were better choices. There is no reason, for example, why they didn't drop the first bomb on un-inhabited area, with the specific statement - the next one's gonna' hit you hard. As it was, it was banking on "we have this bomb, and we have more than one. Trus us on that" - which, yeah, the Japanes of course didn't at first. And even thought the first one was a only-of-a-kind. Until the next one hit. After which they immediately surrendered. If you were invested in keeping civilian casualties low, you could have given them a free demonstration first, and THEN start to target their cities with the next one - they'd probably have given up after two bombs (aka "only" one city instead of two) as well.
But there was another reason why they didn't: To impress the Soviets. Because at that time there were already tensions. And the clear message was "don't fuck with us. If we say we gonna' annhilate your cities, we gonna' do that". Which they did.
Ironically - this was also the reason why American scientists deserted directly from the Manhatten projects and gave the technology to the Soviets, to create a power-balance. Even though these scientists weren't communists at all, and hated having to spend the rest of their lifesin Russia, they were deadly afraid of how a rightwing American gouvernment would dominate the world with these bombs without any counter-balance.
Just another nice example of "showing force" gone wrong.
Yes, the two nuclear strikes were both kinda' justified in the war situation. But - as in most politics - going full confrontational also hits yourself HARD in the long-run, because you don't just project strength - you also show the world you can't be trusted with that strength. In this case - that the rest of the world also needs nuclear weapons to protect themselves from the first-strike trigger-happy Americans.
What if hitting only the one city was not enough after using the first one on a non inhabited area, the Japanese would have thought it a bluff until the Americans actually followed through and even then it took a second one.
It would have meant a land invasion of the two main Japanese islands and the death toll would have been in the millions.
They made the right call, not a good call or a fair call or a nice call but the necessary call and it worked, you can pull your punches if you like but I doubt your opponent will do the same, the Japanese Military at the time sure as hell wouldn't.
Some of the scientists switched because they were communist sleeper agents and had been from the start as the Russians had a pretty extensive network in the US, those that did give the bomb to Russia brought about the Cold War which was a horror show for most of eastern Europe unless you were a member of the Communist party (everyone is equal it's just that some are more equal than others), some of them just did it for the money, plus the Nazis had been working on a bomb and the Russians grabbed them while the Americans grabbed Werner Von Braun and his rocketry team.
It does make me laugh how so many these days think they know better when half of them weren't even born at the time and so many had already died after five years of war, too many people are far too quick to forget or think they know or could do better.
If some of the individuals on this board who like to publicly halo polish had been there at the time making the decisions we would have lost, it's sad to see that kind of zero sum game thinking.
Anyone who honestly thinks that the Americans nuked the Japanese just to frighten off the Russians need their heads examined, they wanted the war to be over and really didnt want to have to invade the two main islands as they knew it would be a meat grinder to end all that came before.
Events never turn out like they do in the films and TV shows, there is no happily ever after or easy way out, there are no heroes in war, only survivors who have to live with the guilt and try to rebuild their lives without the family and friends who didn't make it.
The freedom that everyone takes for granted these days was paid for in blood, the only currency that actually matters when all else fails, they did the best that they could with the information they had at the time.
I will leave it there and wont respond further on this.