The new element here is not just the intensity of the airstrikes and the ground offensives, but also their scope. In the past, ISIS has rarely had to fight on more than one front at a time, so its commanders could move units around, depending on where they were needed. Now, to an increasing degree, they’re all engaged in battle, all the time; they can’t fill gaps or refurbish their supply lines as readily as before.

ISIS has drawn much of its strength from the weakness of its foes. If all the nations that fear and loathe ISIS—which is to say, almost all the nations of the Middle East—could band together, they could win in short order. But the problem is that many of them fear and loathe one another still more.