A thought experiment
Suppose that on the eve of Germany invading Poland Hitler has a debilitating stroke or a heart attack and power is seized by a loose collection of his underlings. They do not attack Poland (high risk, Hitler was the gambler among them) and consequently they do not go to war with France and the UK.
Germany and the USSR continue rearming, so does France, the UK and to a lesser degree, the US.
Japan continues it’s war in China but does not initiate conflict with any of the US and European powers (low upside, high downside risk if there is no war with Germany)
German keeps control of it’s various territories, Austria, Sudeteland(sp), Checkoslavakia, etc .
The world slips into a cold war type arrangement, similar to the US and Soviet Union in 1955, but more dispersed
Proxy wars abound, in a much more complicated way, but no great power conflicts.
The question – does anyone on any side develop nuclear weapons in this scenario? The Manhattan project was insanely expensive and was competing only with other military projects, and had an immediate use. If there was no immediate use, no sense of national urgency and was competing with both civilian and military uses for the funding – would anyone on any side have bothered to develop atomic weapons at that cost, both financial and talent?
This came up on the Lunar Society podcast with Richard Rhodes – he thought that the technology had too much promise to go undeveloped, which I thought too, but after more thinking about it I am no longer sure. It was an obvious choice in a military/war environment, less obvious in a high tension peace environment. The Star Wars program of the 1980s (a very imperfect comparison) would suggest that atomic weapons would not be developed.
Update – I ran this by a group of very smart people, all of whom disagreed with me. I am still somewhat convinced of my position though.