Are there other examples of civilians participating directly in military actions like the evacuation of Dunkirk and if civilians are involved in military actions, do they become enemy combatants that you can kill or not?

So this question was obviously inspired by the movie Dunkirk. So what I was wondering is a two part question. The first is are there other instances of civilians actively participating in a military action, not as support and medical personnel or as spectators like the early days of the American Civil War but actually entering the line of fire to participate in a military action? The second part of the question is what is the policy on targeting them? I don't know if they remain protected as civilians or if they forfeit that by supporting the military. I think the second part of the question boils down to could the Germans have shot at the civilian boats at Dunkirk and been justified? Thanks!