International Relations/The Use of Force
A use of force doctrine is employed by police forces, as well as soldiers on guard duty, to regulate the actions of police and guards. The aim of such a doctrine is to balance security needs with ethical concerns for the rights and well-being of intruders or suspects.
U.S. soldiers on guard duty are given a "use of force briefing" by the sergeant of the guard before being assigned to their post.
"The only difference between lawful force for police and civilians is that peace officers are not given the option of fleeing the scene to avoid confrontation." 
Indeed, soldiers on guard duty will be severely punished for "abandoning their post" if they leave before being "properly relieved".