The Sopwith 1½ Strutter, also known as the Sopwith Two-Seater by the Royal Flying Corps (RFC) and the Sopwith Type 9400 by the Royal Naval Air Service (RNAS) was a versatile aircraft that served in the roles of two-seat scout, or fighter, single-seat bomber, single-seat night fighter and two-seat reconnaissance aircraft. It was also the first British aircraft to sport a synchronized Vickers gun for the pilot as well as air brakes, while the observer was armed with a Lewis gun. The 1½ Strutter got its name from the “W” shaped centre section cabane struts, and the first unit to operate it was No. 5 Wing, RNAS, in April 1916. The RFC’s No. 70 Squadron started using the 1½-Strutter in July 1916, and the aircraft was also used by France, the United States, Belgium, Romania and Russia. In all more than 6,000 1½ Strutters were built, with France building most of them, or around 4,500 aircraft.
The 1½ Strutter was powered by a 110 hp Clerget rotary engine, although it was eventually re-engined with a 130 hp Clerget 9B. The last unit to use the 1½-Strutter was No. 70 Squadron RAF which was a Home Defense unit flying from Goldhangar and Stow Maries in Essex. The aircraft was also used in the Russian Civil War and in the Polish-Soviet war of 1919 to 1921.