(JNS) — For those old enough to remember the images of the last days of South Vietnam, recent events in Afghanistan are shockingly familiar. In each case, a flawed American ally facing a determined foe quickly collapsed once both sides to the conflict realized that the United States wouldn’t lift a finger to help its friends.

Afghanistan was America’s longest war, and sadly, it must go down in history, like Vietnam, as one in which a superpower was defeated by a much weaker enemy. In both instances, there are good reasons to argue that defeat might have been inevitable despite the ski...