Rogue President: What to do?

Oh, perhaps I am thinking the unthinkable, but I wanted to bring it up. It just comes to mind.

What about a military intervention as a coup d'état in America? I realize that there is a lot involved and that the military leaders, (Joint Chiefs of Staff, et al) are pledged to protect and obey the President as Commander in Chief. However, they are also pledged to do so for the country and the Constitution.

Now, even if we consider that their loyalty will remain with their political inclinations, what is the potential for a military action to stop the President? If he put the country in grave danger repeatedly, wouldn't they have to consider acting? Could they? Would they be obliged to intervene? What would the threshold have to be? The use of the nuclear codes could be a rather quick event if nobody were to stop him, for instance, but I am just postulating a series of dangerous moves he could make regarding our military.

The way things I going, I thought I would bring it up for discussion as to pros and cons and to even get more expert opinions from people well-versed in the legal aspects of such a move.