With the establishment of the Defence Forces in 1924, the 18-pounder was the only artillery weapon in Irish service, forming the 1st and 2nd Field Batteries of the Artillery Corps. By the following year, twenty five 18-pounder guns were on hand and three more were delivered in 1933. Additional equipment received by the army in 1941 included four 18-pounder guns. The regular army's field batteries re-equipped with the 25-pounder in 1949 but thirty seven 18-pounder guns were still in use with the reserve FCA. The guns remained in FCA service until the late 1970s, when they were replaced by the 25-pounder and 120 mm mortars.