The Distinguished Service Order (DSO) was awarded to military officers for individual instances of meritorious or distinguished service in war. Recipients usually received it for combat against the enemy. For additional acts of gallantry, a bar was issued.
For services during the Great War, the London Gazette announced the award of the Distinguished Service Order (DSO) to members of the flying services 304 times:
Airmen who received the DSO: 275
Airmen who received a first Bar to the DSO: 27
Airmen who received a second Bar to the DSO: 2