That's not how counterfactuals work. We played Russian roulette and got very, very lucky. Even the hawkish experts agree on this. We've been on the brink of nuclear annihilation a dozen times since WW2 and each time it was random chance that saved us. It's almost enough to make one believe in anthropic arguments.

The grandparent is misquoting von Neumann and taking his remarks way out of context. von Neumann was part of a presidential commission from 1945 that came up with policy recommendations for the post-nuclear age. They accurate surmised that Russia would get the bomb, and that this would lead to what we now call a Cold War, with all the downstream ramifications like constant geopolitical instability from proxy wars. They were 100% right on the money. Niels Bohr called it the "complementarity" of the bomb. It was really remarkable how much they figured out from an understanding of nuclear physics, their experience in the war, and some rudimentary game theory.

They also knew about thermonuclear bombs. von Neumann was instrumental in doing the theory to show it possible during the Manhattan project. A prediction from the commission was that the inevitable outcome of Russia getting the bomb would be a nuclear arms race to develop more powerful bombs, faster delivery vehicles, and hair-trigger firing mechanisms. They predicted nuclear brinkmanship, and the removal of safeguards. They knew it would only be a matter of time before real events, or accidental mistakes led to a nuclear exchange between these two powers. And the longer you waited, the more devastating this would be.

They came up with recommendations: a nuclear non-proliferation treaty with allowances for mutual inspections. A revival of a league of nations to settle disputes. A mutual-defense treaty whose members would be permitted access to Anglo-American nuclear weapons for defensive purposes only. All of these would come to pass eventually, but at the time they were completely rejected (except the UN, although it came to serve a different purpose) by Truman and Churchill. The idea of Russia developing a bomb on a short timescale was seen as ludicrous. The idea of a "Cold War" was science fiction.

But in 1950 the Soviet Union had just detonated their first atomic bomb some months before. They still had a ways to go to ramp up production and make it a practical, deployable weapon. They had the bomb though, and would no longer be willing (if they ever would have) to partake in an arms reduction, mutual defense non-proliferation treaty. The Cold War was suddenly real, and ramping up. Bohr and von Neumann were proven right.

The US had not yet developed the thermonuclear bomb, so the bombs they had were like the weaker ones dropped on Hiroshima and Nagasaki. These were powerful weapons, no doubt, but not fundamentally any worse than the kind of devastation that was already normalized with the firebombing of Dresden, Tokyo, and other cities. Just more compactly packaged. So there was a very brief window where the invasion of the Soviet Union could have happened and would have been successful. How many would have died depends on how long it would take to force a surrender. Certainly hundreds of thousands, likely millions.

So now we get to 1950, and what von Neumann is saying is essentially this: "Look, you political half-wits hacks failed to take action when we warned you five f@&$ing years ago that this would happen, while there was still time to have peaceably avoided this mess. Now millions will die in pointless proxy wars fought between client states in the decades to come, culminating in an eventual nuclear exchange that will kill billions, destroy world civilization, and maybe even the entire human race.

"Or, hear me out, we can put a stop to this right now with a preemptive invasion of the Soviet Union. Millions will die, but millions are going to die anyway, and we will possibly save billions. Stalin kills millions of his own people anyway."

He didn't use those words, but that's a summation of what his argument was at the time. Once again, this advice was rebuffed. The politicians didn't want to start a war the public wouldn't understand. Better, they thought, to kick the can down the road. He then countered with the quote in the grandparent post, which is essentially saying "No, kick the can and you get a bigger mess. Settle it now and fewer people have to die." Better to rip that bandaid off.

It's a calculus of death. But that's no different than the logic that went into bombing Japan to prevent an even more devastating invasion of Honshu. It is sickening and abhorrent, but not necessarily wrong, and it is not genocide.