I think that perhaps we can be trained to the highest degree but in the end we are all just human and with that comes emotions. For example what would happen if you come across a combatant who shoots and kills 5 of you army mates, shoots and wounds you and then throws down his rifle and puts his hands up to surrender...or a person surrenders only to walk up to you with an explosive device strapped to his chest...pretty hard to control your emotions and fear in that split second. The problem is, I feel, is that in most cases of warfare today the other side does not play by the rules and let's face it the Germans and Japs (WW2), Koreans and Vietnamese also didn't play by the rules as well...do we sit in our ivory tower playing by the rules of warfare as we watch our soldiers give their ultimate sacrifice to us?
War doesn't decide who is right or wrong...it only decides who is left!