Does an ethics of war require a view on the nature of war?

One question I have pondered a bit as I've been chugging away on my just war manuscript is whether having an ethics of war requires some commitment as to the nature of war itself. I have written thus far taking the view that it does not - this is mostly in order, I suppose, not to prematurely lose readers who might take exception to my view of the nature of war, and then assume that there's no reason to go on to the account of war's ethics. So I have proceeded, as Walzer and Elshtain and Johnson and other writers do, on the assumption that we know, well enough, the phenomenon of war that we seek to characterize in ethical terms, and do not need for purposes of ethical characterization to commit ourselves to a theory about war and its nature.

This strikes me as a prudent policy for an ethicist, and I don't suppose that I'll change it midstream. Still, I have some questions as to whether it works so very well. I mean, for example, supposing that one had a view of the nature of war that was driven by a strong view of its underlying elements - that violence was strongly biologically, indeed (say), genetically encoded in human beings. If you had some kind of very strong factual predicate such as that, would not your ethical view necessarily be influenced? The most important matters, I reckon, in which the ethical view would be conditioned on a view of the nature of war would be matters of determinism and the will - the belief in genetic predicates of violence and aggression tied to war being the most obvious.

The reason, then, for not wanting to tie one's ethical theory about war too closely to a theory of the nature of war is that most of us, I imagine, don't have a final or strongly held view of the nature of war itself. Maybe some forms of moral realism about warfare do carry such presumptions - Clauswitzian thinking, where it crosses back and forth between a theory of the nature of war and the morality of war, for example - might be the clearest exception. "War is hell" is a view of the nature of war that carries strong normative implications, or might anyway. Some versions of pacifism and nonviolence might also be freighted with a view about the non-moral nature of war - its uncontrollability, for example.

What about theories not simply about the nature of war, but instead about how it arises in human behavior? Theories about aggression and violence and weapons use? Of course, strategically, as a moralist one wants to avoid committing one's moral theory to ultimately speculative and nonfalsifiable theories of the etiology of war. On the other hand, supposing you think that war is what the historian Robert O'Connell, in The Ride of the Second Horseman, says it is - a cultural adaptation, and a late one at that, one which takes the creation of domesticated plant and animal species, the growth of cities, the utilization of the horse, as requirements for the development of what we really mean by warfare - that is, not merely "organized theft," but instead a much more developed, culturally complicated social activity. If you think that, then might it not have implications for your ethical theory about war? About its plasticity in human behavior?