I don't think that war in inherently wrong. I support my country's presence in Afghanistan. Since the advent of liberal democracy, the degree of violent death has decreased exponentially. Yes, when major conflicts occur, they are far more devastating. However, if the same proportionate amount of people died at the hands of their fellow humans in the 20th century as in the pre-modern period, there would have been two billion deaths from warfare. Not 100 million. You can literally see that deaths from violence are decreasing by the decade, world-wide. I don't think that you can say that war is a natural inevitability either, it's too recent a practice to have been shaped by natural selection. If it is inevitable it is because of tribalism and nationalism, that is select ingroups fighting over scarce resources.