Commentary America’s top general in Afghanistan, Austin S. Miller, is deeply worried the United States has lost the war in that region—and he knows best, because he’s on the scene. In a recent conversation with journalists in Kabul, Miller declared, “A civil war is certainly a path that can be visualized if this continues on the trajectory it’s on right now.” But even this grim assessment is optimistic. The real danger is not of a divided Afghanistan, with rival tribes competing for power and dominance, but rather a nation completely taken over by the Taliban. Taliban fighters have been over-running districts in quick succession, not merely in the middle and southern part of the country, where they have always been strong, but even in the north, where the Tajiks and other rival tribes have traditionally been dominant. What this means is that a full U.S. withdrawal, of the sort originally …