What was achieved by the Free State during the Irish Civil War was remarkable. Within a period of less than a year they raised and equipped a standing National Army of nearly 60,000 soldiers, defeating the anti-Treaty elements of the IRA. Using the counterinsurgency framework of Clear-Hold-Build, the author examines, analyzes and explains how the Free State managed to attain this remarkable achievement.Outnumbered at the start of the fighting, the Free State overcame an IRA insurgency by utilizing a number of key concepts that will be explained throughout this thesis. These concepts include the combination of kinetic clearance operations and 'Good Governance' stability actions. They also include; the use of locally recruited soldiers combined with experienced Irish veterans from World War I; the ability to generate, train and equip a new standing National Army to counter and gain combat power over the IRA; the capacity to become an adaptive learning organization, to reform, reorganize and reconsolidate against IRA tactical gains; and finally the ability to foster trust with the local population, enhancing the information sharing nexus and undermining the IRA cause. All of these concepts will be explained and examined through analyzing the successful counterinsurgency campaign executed by the Free State during the Irish Civil War.