I have a general comment to make which finds Megan's argument deficient, but appreciates Nimed's perspective on the U.S and would like to make it here. I would add to his perspective by citing an example from a SEAL in VN. Sometimes when they were approaching a point of the Communists that they were attacking they would come across a disemboweled older woman. The Communists would do this anticipating attack because the impulse of the Americans would be to help the women thus creating an alert and a diversion from their attack.
In any event, the Laws of War which include but are not wholly the rules about prisoners need to be considered. According to these Laws, if one combatant side breaks a law, then the other side can break the law in a compensatory fashion as a demonstration that the breaking of the Laws would not be tolerated. This is the argument that 'allowed,' I think unfortunately, the firebombing of Tokyo or the bombing of Dresden. With Al-Quaida's attack Sept 11, you had a major breach, the killing of 3000 civilians in NY, of the Laws of War. The rough treatment, torture within the bounds of training exercises of our own troops, added the American utilitarian objective to the treatment according to the Laws of War to those who had by their continuing presence in Al-Quaida agreed to the earlier violation of the Law of War against attacking civilian targets without military value.