During 2004 to 2008, The United States Marine Corps (USMC) executed counterinsurgency operations in Anbar Province with the purpose to stabilize one of the most violent areas in Iraq. The Marine Corps successfully managed to suppress the insurgency as violence dropped dramatically in late 2007. What did the marines do in order to suppress the insurgency? Why did violence drop in the province? The Marine Corps approach and procedures have been examined earlier through theories of organizational learning and adaptation. However, there is an absence of studies aiming to analyse the Marine Corps’ counterinsurgency approach through the analytical lens of counterinsurgency theory. Therefore this study has the intention to explain the Marine Corps approach and methods through David Galula’s and Roger Trinquier’s counterinsurgency theories with the purpose of gaining a profound understanding for the counterinsurgency the Marine Corps conducted. The results suggest that a population-centric counterinsurgency approach contributed to the positive turn of events in the province. Furthermore it suggests that continued research ought to focus on the importance of indigenous actors, since the theories used in this study did not fully cover their possible impact on counterinsurgency operations.