First instituted on 28 December 1914 as an award for gallantry or meritorious service for officers with the rank of Captain and below, and for Warrant Officers (NCO's with warrant - at the time, this was only a Regimental Sergeant-Major).

In August 1916 it became possible to award a bar or bars to the MC, for repeated acts of gallantry. A rosette worn with the medal ribbon denoted the bar. All awards of the MC were announced in the London Gazette, usually with a citation, although awards made as part of the King's Birthday or New Year's honours were made for reasons of meritorious service and do not usually have a citation. 37,081 MC's were awarded in the war; in addition 2,992* men were awarded a bar to the MC (that is, they won the MC again); 176 a second bar; and 4 men a third bar.