[10] In 1942, the award was extended to officers of the Merchant Navy who had performed acts of gallantry whilst under enemy attack.

[11] Prior to 1943, the DSO could be awarded to only commissioned officers of the Lieutenant-Colonel rank and above, for 'meritorious or distinguished service in wartime' under conditions of actual combat.

If awarded to an officer ranking below Lieutenant-Colonel, it had to be a case of 'a high degree of gallantry just short of deserving the Victoria Cross'.

[10] Since 1993, reflecting the review of the British honours system which recommended removing distinctions of rank in respect of operational awards, the DSO has been open to all ranks, with the award criteria redefined as "highly successful command and leadership during active operations".

The figures to 1979 are laid out in the table below,[18] the dates reflecting the relevant entries in the London Gazette: In addition, approximately 90 DSOs were awarded between 1980 and 2017, including awards for the Falklands, Gulf, Iraq and Afghanistan Wars, in addition to three Bars.