I don't know, I think lately there's a massive flaw in first-strike and MAD policies. Does it ever really make sense to destroy the world and yourself because an ally(Baltic states for example) or even your own state is being invaded? It's certainly not going to improve your situation even if the alternative is invasion by a foreign power.
A powerful conventional army capable of proportional response is the only realistic deterrent.
The purpose of MAD is to never have to launch a nuke.
The entire point of the doctrine is that any sane person in charge of a country('s military) would never risk getting their own country nuked just to attack another country, so having nukes on your side means that no one else will attack you.
This...does somewhat break down when we end up with people in charge of nuclear countries who are not sane.
A powerful conventional army capable of proportional response is the only realistic deterrent.