Transcript of Conversations among German Nuclear Physicists at Farm Hall (1945) [pdf]

I don't understand why the US doesn't give Japan a pass for Pearl Harbor. At least that was an unambiguous military target.

I found a Quora thread[0] with several answers from apparent Japanese natives that appears to address this.

Some Japanese don't give the US a pass, and Japan's pacificm and anti-nuclear stance can be seen in light of that (see the answer by "Hide Izumi",) as Japan's express policy of not wanting to repeat the evil done to them by the Americans.

Others accept the common rationale that the bombs would have saved more lives in the end than an invasion, and that the Japanese government at the time had betrayed its own people, committed atrocities and had to be stopped.

Others, still, don't really care because it was 70 years ago.

It probably helps a great deal that the US invested money and effort into rebuilding Japan after the war. We didn't want them to turn out like Germany after WW1 and wind up fighting them again in a few years.

[0]https://www.quora.com/How-could-Japan-forgive-the-atom-bombs...

America today is not the America of WWII. We are not saving the world from Hitler today, we are blowing up weddings and causing Europe to be flooded by refugees running from the chaos left in the power vacuum we created. The reaction to this caused Brexit, and nationalism across Europe is again on the rise thanks in large part to our foreign policy.

Indeed, this I believe is the key insight into the stunning success of the Manhattan project. The scientists worked pretty hard as soon as uranium fission and it's details were discovered, Frisch and Peierls critically got all the fast fission concepts right in 1940, see (https://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls_memoran... And Frisch's story is particularly interesting, see Rhodes' book, doing Christmas vacation with his aunt, who just happened to be the first physicist her back in Germany colleague sent his results to right then.... Vs., for example, again from Rhodes' book, a clerical mixup ruining the saving throw for the German effort, the Nazi political types got invitations for the wrong seminar, one on very technical stuff instead of the pitch for atomic stuff (which, if they'd done everything right, they could have pulled off, I think).

But it took a long time to light a fire under the American authorities, and it wasn't until the absolutely critical replacement of his name is a footnote in history with Groves that things really got rolling, on the industrial scale needed, and the scientists and engineers sufficiently focused on the design and execution of the bombs themselves (which for various reasons didn't end up being the afterthought some expected). And he of course picked Oppenheimer to lead that effort, which was opposed by most, albeit he was one of the few uncommitted physicists capable at that level.

These two men organized more than 100,000 people for the industrial production of the required fissionables (90% of the work per Wikipedia), and Grove's drive got those ready in time to forestall Operation Downfall. Heck, they went from the first real test to putting metal on target in 21 and 24 days....

And the design and fabrication of "the bomb" turned out to be massively harder than they expected due to weapons grade plutonium not being suitable for a gun assembly bomb (which is also grossly wasteful of fissionable, if the Little Boy is any guide, as I recall it had 3x critical mass, and a fair amount if it wasn't as pure U-235 as they'd have wanted). Making the implosion concept work was hard, and they got it right the first time....

Read Rhode's book, especially the latter half after the nuclear physics discoveries take a back seat (https://www.amazon.com/Making-Atomic-Bomb-25th-Anniversary/d...) and Grove's autobiography (https://www.amazon.com/Now-Can-Be-Told-Manhattan/dp/03068018...) to learn the organization and management details, they're amazing.

And had much wider effects on the world at large, that we could indeed do such things led to the Apollo program, and of course to too much conceit that "If we can put a man on the moon, why can't we [do something very different and a lot more intractable, probably without even a clearly defined goal]?"

While the Manchurian offensive was big and very successful, the Red Army was massively more effective than they were in 1938-9 when they'd previously stomped the Imperial Japanese Army, they simply didn't have the resources to seriously invade the home islands.

At "best" they would have been able to take a port in northern Hokkaido, which would have been terribly obnoxious after the war, but not by itself strategically significant after they'd taken so many of the islands to the north. Details about this, and the massive resources that would have been required by us to take just Sapporo, can be found in the highly recommended Hell to Pay: Operation Downfall and the Invasion of Japan, 1945-1947 (https://www.amazon.com/Hell-Pay-Operation-Downfall-1945-1947...) I recommend elsewhere in this subthread.

To imagine this was a major factor in the decision, when e.g. Truman's ship to the Potsdam Conference crossed the path of 4 US divisions being shuttled from the ETO to the Pacific is ludicrous. E.g. we're still issuing Purple Hearts from the initial lot MacArthur ordered, which was estimated to be 1/4 of what would be needed for Operation Downfall. This was also not long after the survivors of the Bataan Death March had been rescued, we were very much in a mood of revenge, see Grove's autobiography for a direct citation of this in reference to the bombing of Hiroshima.