The lessons of Afghanistan were purchased at a bitter cost: the war claimed more lives, more years, and more money than any other campaign in NATO's history. Unless the alliance takes those lessons to heart, a war in Syria and Iraq to extinguish Daesh -- the self-styled "Islamic State" -- will be worse. In any military campaign against Daesh, how will we identify effective allies on the ground, who are less pernicious than our common enemy? How will we ensure that neither chaos nor tyranny fill the vacuum left after a successful campaign? Whom will Syrians be able to trust to rebuild their country?