Exactly, exactly, exactly. The doctrine only works if there is "assurance", it is even right there is the name. Would someone with this administration as a geopolitical or military adversary sincerely believe that it would meet a first strike detection with a response in kind? Or would they be convinced enough in liberal fatalism that they would place a nuclear bet that we would just close our eyes and think of England? The problem isn't that MAD doesn't or wouldn't work, it is that is an open question whether there is MAD right now between the US and other nuclear states. Without it, we only have the typical geopolitical and economic factors that prevent war in general. Right now, Russia has no upside in a first strike attack, we still dole out money to them, for instance (half of every dollar we give to Ukraine, even, will by law end up in Russia, as if our "response" to Putin is to give him a raise in his allowance).