Probably worth linking to the estimate by a group of superforecasters who give a 16% chance that Russia uses any type of nuclear weapon in Ukraine.
https://forum.effectivealtruism.org/posts/2nDTrDPZJBEerZGrk/...
https://forum.effectivealtruism.org/posts/2nDTrDPZJBEerZGrk/...
Putin had hoped for that after 2014,but he was in for a nasty surprise in 2022. The probability of NATO to strike back is 100%. It doesn't matter if they destroy the Black Sea fleet or naval bases or do something else, they already communicated to Putin several times that the response will not need to be nuclear but for sure will be painful.
With the current hard-line politics and that absolute hate between the two, there is a hair trigger on that escalation.