Below is an estimated list of the major units deployed within the Multi-National Force – Iraq and other United States military units that were operating in Iraq under the U.S. Central Command (USCENTCOM) in 2009, during the Iraq War. In military science terminology, the description of the units involved in an operation is known as the order of battle (ORBAT). NATO and the U.S. Department of Defense define the order of battle as the identification, strength, command structure, and disposition of the personnel, units, and equipment of any military force.