Not only that, but Japan and South Korea, and a few other nations, have (and long have had) the ability to assemble working nukes in very little time because th

Not only that, but Japan and South Korea, and a few other nations, have (and long have had) the ability to assemble working nukes in very little time because the hard part they have already solved: making weapons grade fuel. I mean, there's a famous nuclear accident in Japan where some workers mixed too much plutonium solution in buckets and it went critical, and that was in the 70s. They have tons of plutonium from breeding reactors. They almost certainly have designs for nuclear devices, and probably even a stockpile of parts. It would be a matter of months to assemble them and the fuel.