When I served in the Army, I was not a civilian. Before my service and afterwards, I have been a civilian. My brother, who worked as a policeman and never served in the military, has spent his whole life as a civilian.
<rant>One of the adverse consequences of SWAT teams and warrior-mentality cops, especially those operating in jurisdictions which have suppressed Second Amendment rights, is to think that they are somehow set apart for the rest of civil society. They tend to place a divide between the police and “civilians.” Well, they’re civilians too, and all of us are also citizens. Moreover, civilian police are public employees who work for the citizenry as a whole. To the extent that there is a divide, it’s between the cops as employees and the rest of us as employers.</rant>
Of course, the military has its own law enforcement agencies. My father served as a Special Agent in Corps of Intelligence Police before WW2 and the Counter Intelligence Corps during the war. However, he never served as a civilian law enforcement officer.