 By the First World War, the guns were obsolete for warship use, but many were re-mounted on merchant ships and troopships for defence against enemy submarines and commerce raiders.In land service, limited numbers were mounted for use as coast artillery.In addition, some Mark IV guns were mounted on converted 40-Pr Rifled Breech Loading Gun carriages for use by batteries of the Royal Garrison Artillery (Volunteers) from the early 1900s.