For here is the gruesome fact: The commanders and combatants on each side have reason to believe that, if they hold out a little bit longer, the other side will collapse—and thus they can gain a few more concessions, and tout something resembling a victory, when they both tumble, exhausted, to negotiate the terms of peace.

Each side probably does have a breaking point. The Ukrainians figure that the Russian forces—many of them marooned and thinly stretched—will eventually run out of food, ammunition, and other supplies, without which they can no longer fight. Meanwhile, the Russians figure that the Ukrainian resistance will eventually run out of steam, cities will fold, and the besieged government in Kyiv will surrender…

It’s unclear how long this can go on. Yet it’s still less clear who can stop it. There is no overriding entity that can step in, knock heads together, enforce a cease-fire, then impose or moderate a political settlement. The United Nations was created to do this sort of thing, but even if it had sufficiently large peacekeeping forces (which it doesn’t), Russia is one of the five permanent members of the U.N. Security Council, so it couldn’t be a neutral party.