In September 2013, Chief of Staff of the Army General Raymond T. Odierno directed the Operation Iraqi Freedom Study Group to research and write an operational history of the U.S. Army’s experience in the Iraq War from 2003 to 2011. This volume, The United States Army in the Iraq War, 2003-2006, is the first of two fulfilling that task. It tells the story of the U.S.-led campaigns to remove Saddam Hussein and his Iraqi Ba’athist regime from power in 2003 and to stabilize the country following those operations. It details the course of the campaigns up to a point in late 2006 when President George W. Bush and other U.S. leaders changed the strategy in Iraq to one that resulted in the “surge” counteroffensive by American troops in 2007–2008. That counteroffensive and the subsequent withdrawal of the coalition forces from Iraq are the subjects of the second volume of this series. In scope, the study group members consciously modeled this history after the Army’s “Green Book” histories of World War II. As the Green Books did, and as General Odierno charged us to do, we focused on the operational level of war. These volumes are narrative histories that tell the story of U.S. forces in Iraq, mainly from the perspective of the theater command in Baghdad and the operational commands immediately subordinate to it. They focus on the decisions and intent of the senior three- and four-star commanders in Baghdad over time.