Instead of employing atomic weapons, the US proceeds with a ground based invasion of the Japanese islands in World War 2. What do you think would have happened and what changes would occur in the modern world?

Actually, I have read that the nuclear bombing of Japan was not as decisive as many think in Japan's surrender. Tokyo's fire bombing was as deadly so losing civilian lives was not something that the Japanese leadership was afraid of. If I remember correctly, the Japanses military knew that they would not win a war that last more than one year and USA uncompromising attitude was not in their plan (they gratly underestimate USA fighting spirit). Japanese econmy was collapsing and the USSR was about to declare war to Japan (they did so in the last months of the conflict), severing their last line of supply.

I honestly think that the nuclear bombing was not necessary to the Allies' victory over Imperail Japan but it had sure hastenend the process and put a lot of fear in to everyone (so not operation Downfall for you). At worst, the USA army would have firebombed Japan into oblivion

What little I recall reading lines up with yabaziou's post above, with the added tidbit (which I can't source and may be misremembering) that projected casualties for a land invasion were ridiculously high, in the hundreds of thousands (military and civilian, both sides).

I'm not convinced that either the nuclear attacks nor a full-scale invasion were needed to prevent Soviet invasion, nor to get Japan to surrender. I also think a bomb dropped over water off the coast at a pre-anounced time/place would have been as good or better demonstration of the power of the bomb.

I think blockading Japan and/or invading Hokkaido could have kept the Soviets away, and/or a discussion with Japan about how they should prefer surrender to potential Soviet invasion.

But a full-scale invasion of Japan by the US could have resulted in a lot more death of both Americans and Japanese, and delayed the peace.

The biggest effect on the post-war, I think, would be on the thinking about nuclear weapons. Without a public demonstration/use, ideas about nuclear weapons would probably have evolved differently, though I can imagine various ways, and have no certainty what the difference would have been. I think it's possible they would have been used later in someplace such as Korea... or perhaps they never would have been used and a similar or even more sober attitude might have developed, if tests got pubic attention but no one had ever dropped one on a city. It would probably take longer for people to know/appreciate/fully understand the radiation effects on populations.

Quote from: yabaziou;900746Actually, I have read that the nuclear bombing of Japan was not as decisive as many think in Japan's surrender.

A friend of mine who is married to a Japanese woman is adamant that the A-bomb had nothing to do with Japan's surrender; it was rather their fear of an invasion by Russia.  As the theory goes Japan saw unconditional surrender to the US as preferable to an invasion by the USSR.

Given that there was an actual coup d'etat planned by the Japanese army to keep Japan fighting to the death, I'm not sure how much credence I give the theory.

Quote from: Skarg;900751I also think a bomb dropped over water off the coast at a pre-anounced time/place would have been as good or better demonstration of the power of the bomb.

That's a common canard by people who don't understand military R&D.

John Toland, a renowned military historian who married a Japanese woman and paid considerable attention both to Japanese sources and to the numerous calamities that resulted from mistranslations (especially into the runup to the war), opined that the nuclear strikes weren't so much the finishing blow as a dandy excuse for the Emperor to step in and surrender, without being overthrown by the die-hard rejectionists.  

Quote from: daniel_ream;900753A friend of mine who is married to a Japanese woman is adamant that the A-bomb had nothing to do with Japan's surrender; it was rather their fear of an invasion by Russia.  As the theory goes Japan saw unconditional surrender to the US as preferable to an invasion by the USSR.

Given that there was an actual coup d'etat planned by the Japanese army to keep Japan fighting to the death, I'm not sure how much credence I give the theory.

Not sure myself; truth be told, what WITH?  Besides, say Russia did carry out the theoretical invasion of Hokkaido -- what, Stalin was going to divert troops he needed to secure his hold on eastern Europe to get some snow covered mountains?

A quarter of Japan's civilian population dies (mostly due to starvation), Stalin gets Hokkaido at least, and probably a good part, such as the northern third of Honshu. All of Korea as well, the Korean War probably becomes the Japanese War. Economically Japan is still a major player today, economically, Korea is Romania.

Quote from: daniel_ream;900753A friend of mine who is married to a Japanese woman is adamant that the A-bomb had nothing to do with Japan's surrender; it was rather their fear of an invasion by Russia.  As the theory goes Japan saw unconditional surrender to the US as preferable to an invasion by the USSR.

Given that there was an actual coup d'etat planned by the Japanese army to keep Japan fighting to the death, I'm not sure how much credence I give the theory.

The Red Army obliterated the Japanese in Manchuria with relative ease. That was the final nail in the coffin for Imperial Japan, not the A-bomb. The interesting part of the whole finale to the war is that Japan was refusing to surrender unconditionally. Since the main condition they were holding out for was keeping Hirohito as a figurehead emperor, all those people were shot, blown up, burned alive or run over by tank treads for nothing, seeing as how MacArthur kept Hirohito in place.

Quote from: The Butcher;900750What little I recall reading lines up with yabaziou's post above, with the added tidbit (which I can't source and may be misremembering) that projected casualties for a land invasion were ridiculously high, in the hundreds of thousands (military and civilian, both sides).

This is Operation downfall : https://en.wikipedia.org/wiki/Operation_Downfall

There was an attempt at a military coup : https://en.wikipedia.org/wiki/Ky%C5%ABj%C5%8D_incident (they even made a movie about it : https://en.wikipedia.org/wiki/The_Emperor_in_August

As interesting all this discussion about was happened is, Nexus is looking for alt history, so I will present this : https://en.wikipedia.org/wiki/1945_%28Conroy_novel%29

If you are looking for other alt WW 2, check this : Uber (super nasty alt with Nazi UberMensch, trigger warning : https://en.wikipedia.org/wiki/%C3%9Cber_%28comics%29) or that : Jin-roh, the Wolf Brigade (https://en.wikipedia.org/wiki/Jin-Roh:_The_Wolf_Brigade)

Jin Roh is actually a very good anime movie, which also part off a wider alt history setting upon which Mamoru Oshii works. There is probably a quite interesting spy focus campaign to do in this setting (maybe with Night's Black Agent ?).

Quote from: The Butcher;900750What little I recall reading lines up with yabaziou's post above, with the added tidbit (which I can't source and may be misremembering) that projected casualties for a land invasion were ridiculously high, in the hundreds of thousands (military and civilian, both sides).

Hundreds of thousands of causalities on each side would be a low projection. Allied casualty estimates  ranged between hundreds of thousands and 4 million casualties. Japanese casualties were estimated to be significantly higher.

Quote from: Bren;900828Hundreds of thousands of causalities on each side would be a low projection.

And people say *nuclear weapons* stress the fabric of space-time

Quote from: Nexus;900744Instead of employing atomic weapons, the US proceeds with a ground based invasion of the Japanese islands in World War 2. What do you think would have happened and what changes would occur in the modern world?

With the Japanese gone, the US would make the island part of the US. Lexus, Datsun, Honda, SONY... things like that wouldn't have happened. Japan would just be a huge-ass military training area for the US to test their new A-bombs on while China watched from across the way.

First off, it would have been a massacre, similar to but larger than Okinawa. Civilians would have been ordered to commit suicide when Americans approached etc (again like Okinawa).

Maybe the Soviets would have entered from the north and Japan would have been split like Germany.

Either way, Japan was NOT ready to surrender without a massive loss of life. They weren't even convinced after the first bomb. It was only when they believed that the only options were to surrender or to let the whole nation, leadership included, go up in flames that they surrendered (and even then after much squabbling).