In the First World War, pilots began to seek out volunteers from the ground staff to fly in the open rear cockpits of their aircraft to help protect them from attack from enemy aircraft when 'scouting' over enemy lines. They often were 'wireless operators' and their armament was a development of the army's Lewis gun.

As, in the 1920's and 1930's, larger aircraft came into service with the RAF, so air gunnery developed; and wireless operators were also trained as air gunners. Wearing the winged-bullet badge on their sleeves, in addition to the 'sparks' badge of the wireless operator they became known as 'WOP/AGs'. They still flew in open cockpits, usually in the nose of the aircraft, using a single Lewis or Vickers machine gun, mounted on what was called a 'scarff ring', which enabled the gun to be moved to follow an attacking aircraft. 

Before WW2, enclosed turrets were being developed by Boulton Paul, Frazer Nash and Bristol Aircraft. Hydraulic or electrical power provided from the aircraft's engines, enabled them to be rotated. The first of these power-operated turrets, fitted with a single .303 Lewis gun, was installed in a Boulton Paul 'Overstrand' medium bomber, which was used by 101 Squadron between 1935 and 1938.

Early in the war, 'mid-upper' turrets were fitted to aircraft such as the Avro Anson, Bristol Blenheim and Boulton Paul Defiant. The wireless was so placed that the Wireless Operator could also be a gunner.

In December 1939, by instruction of AMO A552, the winged-bullet badge was replaced by a brevet denoting an aircrew member, bearing the letters 'AG' and all qualified air gunners were promoted to the rank of sergeant.

Soon, the twin engined Whitley, Wellington and Hampden were fitted not only with a mid-upper turret, but also a rear turret and often a front turret. In these, the American 'Browning' .303 machine gun was installed in either banks of two or four guns.

It was appreciated that Air gunnery was a complicated art, as the gunner had to learn about 'bullet trail', 'drift', 'range finding' and 'harmonisation', in order to maximise his fire power. He also had to know how to correct 'stoppages' on the guns when in flight and to understand, fully, how his turret  functioned.

In 1942 as the fleet of four-engined bombers grew, the demand for air gunners increased and the task was separated from that of the wireless operator, to enable them to be trained more quickly. They were known as 'straight' AGs. However, it appears that Wireless Operators continued to be trained as gunners until c.a mid 1943. Throughout the war all Wireless Operators in the RCAF were trained as gunners and wore the WAG brevet.

The job of the air gunner was to defend his aircraft from enemy fighter attack. This meant that an air gunner had to have excellent night vision and be content to sit in his turret for up to eight hours at a time in freezing temperatures, whilst remaining alert and ready to warn his pilot about evasive action. A lonely life!