No retrospective on the September 11 attacks can escape the bleak pall cast by the tragic events unfolding in Afghanistan today. Despite the enormous financial investment in the country and the grim human costs borne by the United States, its allies, and Afghans over the past 20 years, the US and NATO military missions have ended in ragged, ignominious failure. The question of how well these operations protected the United States and the world from Islamist terrorism remain open. But there is no doubt that the other stated purpose of creating a functioning, friendly, Afghan government and effective security forces that can prevent the reemergence of terrorism from within the country is now forfeit...