You find yourself confronted by an enemy, you have no idea whether he is armed or not, if you want to hang about and take the chance betting on the fact that he not then more fool you, we'll send flowers. If you do not not know whether he or she is armed or not and they are not definitely surrendering, then kill them - it cuts out oven doubt, whatever the case you have "disarmed" them - they can no longer use their arms.