In the immediate aftermath of the 2007 "Surge" of American troops in Iraq, the defeat of al-Qaeda in Iraq (AQI) in Anbar Province was widely hailed as one of America's signature victories. US Marines and soldiers fought for years there, in grinding battles such as Fallujah and Ramadi that define the experience of Iraq. Eventually, the fractious tribal sheiks in that province, with the help of American troops, united in an "Awakening" that dealt AQI a stunning defeat. The Awakening's success argued that the United States could intervene in a war-torn country and, with the right strategy, bring...