Please note that this is not about Nazis with nukes. Indeed the common nuclear Germany world involves nuclear Nazis. However, it seemed to me more likely nuclearization may actually happen if Germany doesn't go down the Nazi route.
This is a what if and me wanting to share a sketch of an alternate history timeline to hold it to some scrutiny and get some pointers as to what to look out for. So far my focus has been on Germany but I intend to work out the timeline to 1947 for the other nations in this world as well. No Nazi Germany is the big deviation in this world so many of the butterflies are in the mid 1930's onward. Imperial Japan is unhindered, Stalin still in the USSR, Chamberlain still is the PM of Britain and FDR is still president. Weimar Germany however, goes down a radically different path as they fall into a de facto civil war and have a basically socialist government by the 1940's that gets the bomb first and upends the whole world.
Indeed, this is that big twist: Nuclear Socialist Weimar Germany.
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How can that be?
Basically the core premise is that without Nazism taking power, Germany retains the likes of Einstein and manages to develop nuclear weapons in the 1940's under the noses of the League of Nations.
The Nazis managed to militarize under the League of Nations watch, having secret weapons programs that spies fail to catch onto soon enough I don't believe to be outside the realm of possibility.
The ideology of this Germany is not too important (this whole concept is in the sketch phase as is). Perhaps it's socialist as Einstein may be more likely to stick around and get talked into helping developing the bomb if it's a Democratic socialist Germany. However I also am not sure if a "democratic" socialist Germany would pursue the bomb. The incentive here is using the bombs as leverage against the League of Nations who had been continuing the reparations for over 2 decades now.
However it is hard to know if the bluff would be called, as while TV would be around the destruction of the bomb would be abstract at best even if Germany did a controlled demonstration of their new invention. And that is where I feel an interesting scenario lies- with the announcement of the bomb and demands the chancellor makes towards the LoN or risk the start of a new world war.
As to why Germany would carry out this radical action, the 30's I pictured still were terrible for them with militia and paramilitary violence being endemic and the Weimar Republic barely stumbling into the 40's with socialists coming to power. Nazi governance was butterflied in this scenario, they were a major militia faction in what was basically a low key civil war in the 30's but never were able to take power. Imagine dealing with that and ongoing humiliation from the LoN. The need to gain leverage was strong and the chancellor here had a gamble to make.
It's a sketchy concept so I'll probably need to research how they are able to build and test the bomb, circumvent regulations put on them by the treaty of Versailles (easy enough) along with keeping British and French spies from knowing about the program soon enough. This is a Germany that manages to retain many of its major nuclear researchers despite the instability of the 30's, imagine Einstein and Schumann working together in Germany on a Nuclear project.
The implications are huge in this world, in more ways than one. Einstein's legacy would be different, the world's relationship to nukes is totally different and Germany's post war resurgence is rather different. However, what would remain the same is the League of Nations being remembered as a failure.
Thoughts?
Update: This is very much a sketch. For instance with even early look ups I've been thinking that Germany being an obvious mess in the early 30's would butterfly chamberlain.