That is a darned good question! The first half that oath is to obey the Constitution. The 2nd half is to obey the President ... even a rogue President who is trashing the Constitution. There is direct conflict in the oath itself. My gut feeling is that if some rogue President violated the Constitution to the point of causing a general armed revolt, those in the military would be forced to pick sides, and there would likely be a revolt within the military itself. Most people in the military (I think) are true patriots. It is a different story for the top brass, many of which are aligned with the deep state. I think most in the military would regard the first half of that oath to take precedence over the 2nd half. If I am wrong, it is going to get very bloody indeed. If I am right, there will be a whole lot of deep state top brass getting summarily executed by their own troops. I believe (correct me if I am wrong) that any retired military officer can re-activate if called upon. Most of those are NOT aligned with the deep state. It could get very, very interesting.