The General Service Medal (GSM) was first introduced in 1918 as an Army and RAF equivalent to the Naval General Service Medal (NGSM). The medal is used in place of a specific campaign medal, with clasps added to the medal to denote the campaign.
In 1962 a modified General Service Medal was introduced which replaced the 1918 GSM and the NGSM.
Post 1962 Clasps issued with the medal include Borneo, Radfan, South Arabia, Malay Peninsula, South Vietnam, Northern Ireland, Dhofar, Lebanon, Mine Clearance, Gulf, Kuwait, Northern Iraq and Southern Turkey.
The institution of any new clasps for the GSM was discontinued on 31 December 1999 on the introduction of the Operational Service Medal on 1 January 2000.