Our military is not going to be part of an unconstitutional coup. Its doctrine and training keeps it from ever wanting to. Even if it did, it cannot sustain itself without top-down reserve activation. The design of the force, since Viet Nam, has been deliberately organized to break down regional and class differences—that’s the Powell Doctrine. Any large scale operation marries Active Duty, National Guard, and US Army Reserve into predetermined, interdependent, combatant commands.
This was done to prevent the “disinvolvement” that led to the 1960s anti-war movement, but it also makes a War Between the States impossible. A bizzaro President can do a lot of harm, but a bizzaro Commander in Chief will find he has nothing to command.