The military and police swear an oath to defend the Constitution against all enemies, foreign AND DOMESTIC.
The Constitution has many, many divisions! And the tens of millions of us who took the oath might remind these would-be tyrants that our oath did not come with an expiration date.
I am reminded of a scene from BattleStar Gallactica....
Roslin: You have committed me to holding elections within the year.
Apollo: Madam President, with respect. You are serving out the remainder of President Adar's term. When that term is up, in seven months, the law says, there is an election. I only committed you to obeying the law.
Adama: You sound like some kind of lawyer.
Roslin: This is unacceptable.
Apollo: I swore an oath. To defend the articles. The articles say there is an election in seven months. Now, if you are telling me we are throwing out the law, then I am not a captain, you are not a commander, and you are not the president. And I don't owe either of you a damned explanation for anything.