The strategic demands of a great power war with a peer-adversary—the high-end conflict—will inevitably push decision-makers to the pale of that which is ethically permissible. We have seen it in the two great wars of the 20th century. In the next great power war—and one hopes it never comes—western states will put their strategic and operational capabilities to the test. But such a war will also test the moral will of their citizens—the people in whose name the killing and dying will take place.