Any action? Lets look at some specifics and ask which ones should count as murder. A reasonable person might see a different degree of justification in each case.
A person wielding a gun is running and firring their weapon towards a solider. The solider shoots back and kills them.
A boat full with military weapons enters an areas which marines are defending and refuse to turn back. The marines sinks the boat.
A tank drives into a town. The Solider defending the civilians attacks the tank and the tank driver dies in an explosion.
A bomb plane that drops bombs on military facility with tanks, airfield with bombers on them, and docks with military ships.
A bomb plane that dropping bombs on a factory that produce tanks and guns, killing workers.
A bomb plane that fire bombs on housing districts to demoralize the population.
A person is driving down the road in uninhabited area, and a solider sends a remote missile.
A person is celebrating a wedding in their own house, and a soldier sends a remote missile to kill everyone in the wedding.