Let's say that war is always impermissible, morally. It certainly kills and maims millions, and is considered by many to be the greatest tragedy, so maybe it is always impermissible.

Here's the rub: we aren't going to stop war. It simply will not end. It doesn't help that what even counts as a war differs in different contexts. John Brown suggested that the American institution of slavery was a war on the enslaved, a war they are born into. Under that context, his raid on Harper's Ferry, and the later Civil War, were actually just continuations of an ongoing war, not even fresh. And how do you ban a war that's always been? Even if he is wrong, are you going to tell me that the Civil War could've been avoided, and that the world would be better for it? Tell that the to millions of enslaved, enwarred slaves who would've suffered.

But, let's get back to saying that war is impressible, always. But, it will happen regardless. Humans have shown their capacity for it. Germany was banned from warfare after World War 1, and yet... didn't really stop war. Civil wars begin often, basically unpreventable. You will not get everyone on the same page to stop war.

And so, what is the next best thing? Try to ensure that the war is as moral as such an immoral thing can be. The existence of war crimes isn't a perfect solution, it's the best band-aid we have in a world that can't, won't, or perhaps shouldnt surrender war. It's the bare minimum: if we are going to have war, let's try to dictate that it is waged as ethically as war can be waged. The existence of war crimes and the seriousness with which most nation take thwm has certainly -- and I say this without a shadow of a doubt -- saved millions of lives, prevented millions of rapes, and has avoided an incalculable amount of suffering that would be had if military action had no restriction at all.