IMO Self Defense in the Civilian world is different from Combat in the Military.
SD with a civilian is usually a last resort, as you would first try to avoid a confrontation. In SD you don't go busting into a house to engage badguys; instead you actually avoid it unless there is no alternative (you are trapped or trying to save a loved one).
With military combat, if you are trying to gain ground or territory i.e. the enemy encampment or whatever and there are armed guards patrolling or in the front gate, you can engage them from a longway without necessarily being in real danger. just my thought process, correct me if i'm wrong.
otherwise combat in the civilian (non-military) world is mostly done by LEO's. A plain civilian would not go around looking for rapists or thieves.