The Sigrist Bus first flew on 5 June 1915 and although it set a new British altitude record on the day of its first flight, only one was built, serving as a company runabout.

Like the Sigrist Bus, each of the upper wings (there was no true centre section) was connected to the fuselage by a pair of short (half) struts and a pair of longer struts, forming a "W" when viewed from the front; this giving rise to the aircraft's popular nickname of the 1+1⁄2 Strutter.

The aircraft had a variable-incidence tailplane that could be adjusted by the pilot in flight and airbrakes under the lower wings to reduce landing distance.

[10][11] The prototype two seater flew in December 1915 and production deliveries started to reach the RNAS in February 1916.

Since the Battle of the Somme was planned for the end of June and with the RFC having a shortage of modern aircraft, it was agreed that a number of Sopwiths would be transferred from one service to the other, allowing 70 Squadron to reach the front by early July 1916 with Sopwith-built 1+1⁄2 Strutters, originally intended for the Navy.

The period of German ascendency known as the Fokker scourge was over and the 1+1⁄2 Strutter's long range and excellent armament enabled offensive patrolling deep into German-held territory.

By January 1917, when 43 Squadron arrived in France, the 1+1⁄2 Strutter was outclassed as a fighter; a more powerful 130 hp (97 kW) Clerget 9B improved performance slightly but too late to reverse the situation.

[18][19] Like other early Sopwith types, the 1+1⁄2 Strutter was very lightly built and its structure did not stand up very well to arduous war service.

It was far too stable to make a good dogfighter and the distance between the pilot and the observer's cockpits impeded their communication.

[18] The type's long range and stability were good qualities for a home defence fighter and it served with 37, 44 and 78 squadrons.

Most of the 1+1⁄2 Strutters supplied to home defence units had been built as two-seaters but many were converted locally to single-seaters to improve performance.

The RNAS and the RFC (and after April 1918 the Royal Air Force [RAF]) used the type as a trainer after it had been withdrawn from operational service and like the Sopwith Pup, it proved a popular personal aircraft for senior officers.

During the war, several 1+1⁄2 Strutters that were interned after landing in the Netherlands were purchased for the Dutch Luchvaart Afdeeling.

Over 100 1+1⁄2 Strutters were also built in Russia by Duks and Lebedev,[22] supplemented by large numbers delivered directly from Britain and France.

The American Expeditionary Force purchased 384 two-seat Strutter observation aircraft and 130 single-seat bombers from France in 1917–18.