While the paper membership of the IRA, carried over from the Irish Volunteers, was over 100,000 men, Michael Collins estimated that only 15,000 were active in the IRA during the course of the war, with about 3,000 on active service at any time.
På papiret talte IRA over 100.000 mand fra Irish Volunteers, mens Collins vurderede, at kun omkring 15.000 faktisk var i tjeneste i løbet af krigen med omkring 3.000 i fast tjeneste.