I’ve been thinking lately of the tragic consequences of nuclear weapons being developed right at the end of WWII - tragic not only in that that were used but also because their invention triggered an enormously costly arms race between the superpowers.
Does anyone have insights into the relationship between (a) the set of factors that contributed to nuclear weapons becoming conceived and then realized and (b) the set of factors that led to WWII?
Obviously war triggered weapons research and all that, but more broadly was there something inevitable sociologically or scientifically about the industrialization process that contributed to this dual development? Could realistically WWII have happened the way it happened (up to 1945) without the nuclear sciences following suit?
From our vantage point they seem like two parts of the same progression but perhaps they are more coincidental than they appear?
There was nothing inevitable about the creation of nuclear weapons during World War II. Only one country got anywhere close to making them (the United States), and if it had made a few slightly different decisions, or had slightly different circumstances, it wouldn't have made them either. So one can definitely imagine a World War II without atomic weapons having been built — other than the United States, it was actually what happened!
What the Manhattan Project accomplished was just barely possible given the scientific knowledge they had when they started. They were taking what was essentially (literally) table-top science and expanding it to an entirely new industry over the course of less than 3 years. In typical scientific-technical development, that usually takes at least a decade. So they basically, by sheer force of will and massive expenditure of resources, squished ten years of development into about 2 years of time.
The reason they did this was more political than scientific; the science pointed towards its possibility (though only just barely, and it was in fact a lot harder than they expected it to be), but what motivated them down this path was fear of a Nazi nuclear program (which turned out not to be anything worth worrying about, but it took them awhile longer to learn that). This fear, plus some preliminary results that hinted at the plausibility of making a bomb in a short amount of time, motivated a few very specific people in the United States to push for a full program (notably Vannevar Bush, James Conant, Ernest Lawrence, and Arthur Compton, among others). If those people had not been in positions to actually make this thing occur — notably Bush, who had FDR's ear and who had the Office of Scientific Research & Development at his personal disposal — the project would never have gotten off the ground.
If they had instead concluded, as the Germans did around the same time, that nuclear weapons was a problem for a future war, and not something that was likely to emerge during World War II, then they also likely wouldn't have made much progress towards it.
The interesting question that sometimes get asked is, if the US had never built the atomic bomb during World War II (e.g., it had never gotten further than the work by Section S-1, the Manhattan Project's pre-production predecessor), when would atomic weapons have been made, and under what circumstances? It's impossible to know, of course, but it's likely they would have bene developed by the early 1950s, though who would develop them first is unclear. And without the horrors of Hiroshima and Nagasaki, what would instead the first use of the weapons have been? Would they have been understood as world-changing, or just a new form of armament? Would that world be more dangerous, or more safe, than the one we ended up in? Would there have been a Cold War, and would it have been better or worse than the one we ended up with? It's impossible to know these kinds of things, of course, but it makes for a set of provocative questions to ask.
There's plenty in our FAQ about the development of nuclear weapons; in particular, the top two AMAs with /u/restricteddata may be of interest to you.