Almost as soon as Saddam Hussein's regime collapsed in 2003, it became apparent to U.S. commanders that a second deployment of Marines to Iraq would be necessary to conduct security and stability operations. This monograph recounts the first two years of this second deployment during which Marines were responsible for Iraq's cast al-Anbar Province. It focuses on I Marine's Expeditionary Force's deployment in 2004 and II Marine Expeditionary Force's deployment in 2005, and focuses on planning, counterinsurgency operations, and efforts to build civil-military relations with the Iraqi population. The first and second battles of Fallujah and the battle of an-Najaf are also highlighted.