I think he actually did what Bob Woodward is claiming he did. But I don’t think he did it because he honestly thought that Trump was demented and would start a nuclear war. I don’t think he ever thought that, and just trotted it out as a rationalization. In reality, Milley’s problem with Trump wasn’t bellicosity, but the total opposite. Milley didn’t want Trump to enact his staged and carefully planned exit from Afghanistan, because not being engaged in Afg any longer would deprive Milley of opportunities for trinkets. So he strapped up with his Beijing counterpart probably to create a path to where he could engage in some sort of blackmail or extortion against Trump, or at least hurt Trump’s efforts against Beijing.