PUT THIS IN YOUR PEACE PIPE AND SMOKE IT: Lots of people these days are writing about the moral questions of war (when may we threaten to use force, when may we use it, how much may we use, to what lengths must we go to avoid civilian casualties), but but Victor Hanson gives us a primer on the amoral history of war: why wars happen, why they begin, why they end. And it turns out that the amoral history of war informs the moral debates about war.
Fact: enemies read restraint as weakness, not mercy, and repay it with aggression. Fact: negotiations don't end war, material, physical, and emotional exhaustion of one side does. Fact: sometimes people fight because they're aggrieved and oppressed, but sometimes they fight for honor, wealth, or sheer meanness. So it might seem moral to exercise restraint in the face of attack, but you invite more attacks, more deaths, more destruction, which makes restraint seem pretty immoral. It might seem moral to thrash your enemy, but show mercy and let him go; but he'll just rest a spell, then come back at you and kill more people; which makes limited war seem pretty immoral. It might seem moral, when attacked by an enemy with plausible historical and moral claims, to see those claims as "root causes" and try to make peace by satisfying those claims. But your appeasement will teach your enemy that war really can improve his position and he'll see your goodwill as weakness, both of which will invite more war, more death, more destruction. Which makes appeasement seem pretty immoral.
How does Hanson know this? It's history.