In 1939 a requirement was issued for a gun that was capable of firing a 90lb shell 16,000 yards and that weighed less than 5 tons, the result was the 5.5" medium gun. The weapon was to be as up to date and as advanced as possible but this lead to some teething problems which resulted in simpler more effective solutions being used. The carriage was of two wheeled, split trail type and a quick loading gear was fitted so that when the gun was fired at high elevation a lever was pressed which swung the cradle down.
It was not until 1942 that the first guns were in action and initially they lacked range but this was solved by the introduction of an 80lb shell, the weapons were highly successful and were used throughout the rest of the war.
The 5.5-inch Gun was one of the two British medium guns of World War 2, which both used the same carriage (the other was the 4.5-inch Gun). It first entered service in 1942 replacing 6-inch Howitzers in medium regiments. It had limited service in Indian regiments and equipped a South African and three Canadian regiments in Europe. It was popular and recognised as an effective gun, however, there was a problem with bore prematures, particularly in Burma and in late 1944 some 5.5-inch were temporarily replaced by old 6-inch howitzers in that theatre. Initially it had a 100 lb shell but later in the war an 80 lb shell was introduced and this eventually replaced the 100 lb. It left British service in the mid-1970s, UK last used them operationally in Borneo and Radfan in the mid-1960s and the last round was fired in UK was in 1995. Its last operational use seems to have been with the South African Defence Force in Angola in the 1980s. In European countries it was referred to as the 140-mm (or 14-cm) gun.