"The military war in Iraq ended in 2008, although political conflict among Sunnis, Shi'ites, and Kurds will continue for decades. At the same time, the war in Afghanistan has heated up, with more American troops committed to battle. This article, based on 15 extended trips [Bing West] made to Iraq and interviews [he] conducted with 2,000 Soldiers and Marines, reviews the causes of the turnaround in Iraq and their importance for doctrine development and for success in the war in Afghanistan. From 2003 through 2008, two separate fronts accounted for about two-thirds of all American fatalities. In the west, the Sunni province of Anbar emerged as the heartland of a sectarian resistance that was gradually taken over by Al-Qaeda in Iraq (AQI). Anbar accounted for 42 percent of all U.S. fatalities in Iraq from 2004 through 2006. To the east, the Baghdad region accounted for 27 percent of the fatalities in 2004-2006. [...].. So by mid-2006, the coalition was losing on both fronts. In Anbar, according to an on-scene assessment, Al-Qaeda controlled the population. In Baghdad, a civil war was raging and the Sunnis were being driven from their homes. Yet, a year later the tide of war was flowing in the coalition's favor. What happened? Two events changed the course of the war: the 2006 Sunni Awakening in Anbar and the 2007 surge in Baghdad. The Awakening was the critical enabler for success of the surge."
Military Review: https://usacac.army.mil/CAC2/MilitaryReview/
Military Review (March-April 2009), p.2-12