Its unusual layout had a small gunner's nacelle mounted on the upper wing for an all-round field of fire.
In early 1916, the British War Office drew up a specification for a multi-seat escort fighter to be powered by one of the new Rolls-Royce Eagle engines, intended to protect formations of bombers from German fighters, with an additional role of destroying enemy airships.
[1] While the specification did not require high speed, a good field of fire for its guns was essential,[2] while the secondary anti-Zeppelin role demanded an endurance of at least seven hours.
[1] The Sopwith proposal was modified from an existing design for a two-seat triplane, with a nacelle for a gunner added to the upper wing.
The deep fuselage housed the pilot and a second gunner to guard the aircraft's tail.