I think instead anyone paying for anything, we should grow the **** up and realize that the world doesn't work like a fairytale with bad guys, good guys and explosions.
War happens, people kill each other for really outré or understandable reasons, and it will keep happening unless we do something about those reasons.
Trying to enforce a morality or joining a fray with this morality on this shield won't achieve peace - it will merely be a good propaganda back home while your troops will enforce the objectives their generals set them.
You think we should give up, then, and abandon the Hague and Geneva Conventions, perhaps use them as toilet paper. It's really rather pathetic to hold that belief in this day and age, but never mind that.
You brought up WW2. Okay, fine. I'll play ball. The destruction of cities you were so quick to bleat about makes an excellent case in point; the actions taken then by the Western nations so shocked and horrified them that they have never come remotely close to duplicating them. Delibrate bombing of a civilian target is pretty much unthinkable to the Western military mind because it is unthinkable to the population at large. If you want to be more cold-blooded about it, there are reams of statistics and evidence that the Blitz, Bomber Command's night area bombing campaigns, the USAF's area bombing campaign against Japanese cities in 1944-1945, or even the Zepplin raids against British cities in WWI, accomplished absolutely nothing of value. The only "area" attacks, which in the end is a polite way of saying they were aiming for standing buildings, that accomplished anything meaningful was the use of the atomic bombs on Hiroshima and Nagasaki. Going nuclear is not and hopefully never will be a viable option again. Back in 1864 and 1865 when Sherman marched to the sea and tore the place up as he went, then it had a purpose of sorts because there was so very little infrastructure to begin with. In the end it was counterproductive though; even a hundred and forty years later, long after all the physical evidence of what Sherman did is gone, that wound has not completely healed. And even Sherman knew better than to delibrately attack purely civilian targets; no one ever made a directed terror campaign against the people. Today, what the March to the Sea did could not be accomplished again. We have come too far and tasks that could only be accomplished with specialized facilites then, like casting rifle barrels or making bullets, can be done in your garage with ease today, without a lot of preparation. The targets that made the March to the Sea effective have become too many and too nebulous.
War is, in the end, a barbaric institution, and it always will be. To be cold-blooded again, it is also completely inevitable. We have fought since before we were even recognizeable as humans, and it took the atomic bomb and the threat of seeing your country vaporized in a series of white flashes to make the major powers of the world stop making war on each other directly. We will never stop fighting. This is reality.
Yet though we know war is barbaric, this is no reason to be barbaric in waging war. If we accept that it is inevitable, it is in our best interests not to be. Not only is it is demonstrably useless and purposeless to wage total war such as was done in WWII, but as you've already demonstrated for me simply by bringing all that up, the wounds run deep. Parts of Europe still remember rivalries and wrongs dating back to the Dark Ages strongly enough to use them as a pretext for violence, actions which almost certainly pale in comparison to anything done in the World Wars. By being brutal you set yourself up to reap the whirlwind at some later date; by being brutal you also make your task harder as more people will rise to oppose you. And while that was more of a laughing matter about a century ago, in today's world where firepower has become compacter and more mobile this is a big deal. Even a child can kill many today, given an AK-47 with a single clip.
Like every human political institution, the rules of war do not exist simply because they sound good. They were made because they serve a tangible purpose to both the victor and the vanquished: life will go on with as little disruption as possible. This is a worthy goal for many reasons, and most of them are really not altrustic at all. You can't tax the dead and they can't work for you, they just take up space and pose a health hazard. In Eastern Europe during the days of the USSR, the Russians could at least
pretend they were putting down a rebellion, and by oversight of someone somewhere rebels against the established order have no rights. Here and now, they lack even that slender reed to support what they are doing.