The plane was designed by British Sopwith Aviation Co. Taking into account the flaws of Sopwith Camel: bad forward and up visibility, difficulties of handling the plane with rotary engine the engineers were given a task to built a fighter with inline engine. Design featured compact lay-out of pilot seating, fuel tanks, machineguns and engine. Radiators were moved to the sides of the fuselage behind the cockpit. Pilot head was in the hatch of the top wing. First trial flight was made in May 1917. Along the head factory several others were manufacturing it: Darracq, Hooper, SACA. By the end of the war 1532 planes were built.
First combat testing was carried out by British N56 squadron June 13 1917. Several design improvements followed. In January 1918 N19 squadron received first examples. Dolphin was used to engage enemy fighters and balloons, especially at high altitudes, where it was superior to Sopwith Camel. It was also used to bomb and strafe ground targets.
Pilots noted good balance of controls, perfect visibility up and forward, but lower semi-sphere was hidden by lower wings and engine cowling. Being as maneuverable as Sopwith Camel, but with speed and climb rate equal to S.E. 5a the plane was a formidable opponent. Pilots often complained about crumpled cockpit and tendency to nose-over at harsh landings. For a short period of time French and American pilots flew these aircraft. It took part in battles over the Western front.