The Short Type 320 was designed to meet an official requirement for a seaplane to carry a Mark IX torpedo.

When the torpedo bomber went into production, it was powered by a 320 hp (238 kW) Cossack engine which was the origin of the name, Type 320.

[2] At the same time as Shorts was designing the 310 Type A torpedo bomber, it produced a similar design for a patrol floatplane, powered by the same Cossack engine and using the same fuselage, but with equal-span three-bay wings, instead of the uneven- span wings of the torpedo bomber, known as the Short 310 Type B or North Sea Scout, and two prototypes were ordered.

[9] In February 1917, 25 aircraft were ordered, and before the end of April 1917, examples were delivered to the Royal Naval Air Service in Italy.

The first operational use was on 2 September 1917, when six aircraft (five with torpedoes and one with bombs) were towed on rafts fifty miles south of Traste Bay to enable them to attack enemy submarines lying off Cattaro.