The National Army, sometimes unofficially referred to as the Free State Army or the Regulars, was the army of the Irish Free State from January 1922 until October 1924. Its role in this period was defined by its service in the Irish Civil War, in defence of the institutions established by the Anglo-Irish Treaty. Michael Collins was the army's first commander-in-chief until his death in August 1922.
The army made its first public appearance on 31 January 1922, when command of Beggars Bush Barracks was handed over from the British Army. Its first troops were the Pro-Treaty IRA—those volunteers of the Irish Republican Army (IRA) who supported the Anglo-Irish Treaty and the "Provisional Government of Ireland" formed thereunder. Conflict arose between the National Army and those that opposed the government of the Irish Free State namely the anti-Treaty components of the IRA. On 28 June 1922 the National Army commenced an artillery bombardment of anti-Treaty IRA forces who were occupying the Four Courts in Dublin, thus beginning the Irish Civil War.