It saw active service during the First World War on the Western Front in 1917 and 1918 as part of an Army Field Artillery Brigade.

A second line battery, 2/1st Glamorganshire RHA, served in England and Ireland before being broken up in January 1917.

)[5][6][7] The battery was equipped with four[1] Ehrhardt 15-pounder[8] guns and allocated as artillery support to the South Wales Mounted Brigade.

2nd Line units performed the home defence role, although in fact most of these were also posted abroad in due course.

[9] The 1st Line battery was embodied with the South Wales Mounted Brigade on 4 August 1914 at the outbreak of the First World War.

)[17] (that is, before the field artillery brigades of the Territorial Force divisions were numbered in a single sequence).

[9] The pre-war Territorial Force infantry divisions were generally[c] supported by four field artillery brigades.

[19] The Glamorganshire RHA's wooden memorial board listing the 56 men who died in World War I, and their former commanding officer, Brevet Colonel T.J. David, DSO, OBE, TD, who died on 6 November 1926, is in St Mary's Church, Margam.