Interesting article about nuclear proliferation:
https://jacobitemag.com/2017/11/20/independence-games/

tl;dr is that it happens at an exponential rate, makes the playing field a lot more complex than just two-sided MAD and newcomers to the nuclear club are unlikely to give up their weapons (as there's a correlation between WMD disarmament and regime fall) and more likely to use them agressively.

pic unrelated