The Allies would have won without the superweapon though (remember, Hitler had already surrended and Japan was clearly on the ropes well before Hiroshima), and the jury is still out in whether it even sped things up.
It took 5 days from the 2nd bomb to surrender, and many historians think the Soviet Union's simultaneous declaration of war was a more significant factor.
This theory is debunked by the two books, written by two different historians, which go into it in great detail.
The second bomb made it clear that the first one was not a one-off, and that the US was going to nuke the cities one by one. The Japanese also had intelligence (that turned out to be false) that Tokyo was the next target.
I've read a couple accounts by anti-nuclear activists who held that the USSR was the reason for the surrender, but if you compare those accounts with the ones written by historians, the former are crackpots.
An invasion of Japan would be an absolutely massive operation (see D-Day) and the USSR was in no position to mount one.
For anyone who wants to understand this debate better, the popular and academic Japanese record goes under the title “Japan’s Longest Day”.
There’s a minute-by-minute historical analysis[1], a 1967 film[2] (starring Toshiro Mifune! Gotta find this one…), a 2015 remake[3] of the 1967 film, and apparently a forthcoming graphic novel[4].
Fundamentally, the idea of “Japan” making a decision to surrender the way (say) Truman made the decision to drop the bombs is a misleading framing.
At this time, political, military and—crucially—effective police power in Japan was distributed among individuals and groups, notably the young officer corps, with very different motivations, beliefs, and principles.
The atomic bombs, the Russian invasion, the particulars of the negotiations with the US over terms of surrender… all were “merely” external forces influencing a chaotic, unstable equilibrium.
Ultimately, in some combination those forces tipped the center of that power from one equilibrium: “The war is lost, but if we surrender now internal forces will destroy Japan as a nation even if the Allies don’t.”
…to another: “The Emperor must make an extraordinary intervention to end the war immediately.”
Greetings from Ukraine, country at war with Russians, who thought they are genuine descendants of USSR.
Long before Ukrainian war, I've many times talked with Russians about bombs used on Japan.
And now I must say you very important thing - Russians are so crazy anti-humanists, that this really could be reason for fears of Japanese about USSR invasion.
To be honest, I think bombs was enough to intimidate Japanese, but I think, even without bombs, Russians behavior at war, with US Land-lease technical/economical support would be enough to convince Japanese to surrender, may be later, sought.
The has been a ton of debate since the war over whether Japan would have surrendered, and if so how early. The concern at the time, and it has always seemed reasonable to me, was that the Japanese were committed to fighting to the last person and to make them surrender through combat on their home turf would have killed many, many more than the two nukes did.
I don't raise that as justification and personally wish we were never stupid enough as a species to build such a weapon, but we tend to be that stupid. I do, though, agree that we likely would have lost more people on both sides and for Japan that number still would have included a large number of civilians.
Oh I didn't meant to imply that I personally see the nukes as having been reasonable or worth it.
Frankly, I don't know how one could ever make the decision that killing 100,000 is "worth it" and I hope I never have to.
Personally I think we should never have tried to invent the nuclear bomb to begin with, avoiding the decision entirely. I understand the whole "but then the enemy would have it first" argument, I just don't buy it. Sure, maybe the "enemy" would go on to invent it but that's a burden they'll have to bear.
Sometimes standing on principle includes dying on principle, we seem to have lost the importance of all that along the way. I chalk that up to the increase rate of invention making it too scary to take a step back, even for a moment, to decide whether we should do something that we know we can do.
I always saw the atomic bomb as more of a defensive rather than offensive tactic. We were super worried about the Germans getting there first and wanted to ensure we could respond in kind of they did
You either have no knowledge of the topic or have some secret source of information that has evaded the world's historians, because it is a fairly acknowledged fact supported by both Allied and Japanese sources. Japan didn't even surrender after the first bomb was dropped.
I think there's nuance here that gets lost in the retelling. From what I learned of it in a university course dedicated to many aspects of the topic of that bomb, there was a demand of /unconditional/ surrender but Japan wanted to keep their emperor. The emperor was really more of a cultural and spiritual persona than a political one, but regardless the US gov't. insisted on an unconditional surrender, including dethroning the emperor. I think there was an offer of surrender by the Japanese if they could keep their emperor. I don't have proof handy and I'm not inclined to dive down that particular rabbit hole right now so I hope someone can support or correct this.
I vaguely recall hearing something similar, with the reasoning being that there was a fear of future hostility enabled by Emperor driven fanaticism. That said, I've also heard that there wasn't really enough time given for a response after the first bomb, and that it was largely a political move to claim they'd offered an initial surrender - and that the goal was always to drop two bombs, partly because they wanted to test out different aspects of their designs.
