Its no secret that the military was ordered to ignore all orders from Nixon I believe from midnight til the next day when he left and Ford was sworn in. It may have been unconstitutional but Schlesinger put it in play.
Oh yeah. I’m trying to remember which of Nixon’s lieutenants told the Joint Chiefs, “The president is depressed and drinking heavily. If something militarily significant happens, call me.” I don’t consider that terribly out of line. During Vietnam, he was talking wild stuff including nuclear weapons to convince the Russians and others that he was crazy. It worked, better than he hoped even.
As far back as the Kennedy and Johnson Administrations, there have been periodic purges of conservatives in senior military positions. For example, the dismissal of Generals Edwin Walker and Curtis Lemay. Obama was notorious for his mass dismissal of hostile senior officers. Unfortunately, Trump has not done a counter purge of left leaning military officers, something wholly in his purview. Hopefully, he will not regret this.