The departure of the last U.S. troops from Iraq at the end of 2011 left a broken country and a host of unanswered questions. What was the war really about? Why and how did the occupation drag on for nearly nine years, while most Iraqis, Britons, and Americans desperately wanted it to end? And why did the troops have to leave? Now, in a gripping account of the war that dominated U.S. foreign policy over the last decade, investigative journalist Greg...