264 Squadron was first formed during the First World War, from two former Royal Naval Air Service flights, No.

On 8 December 1939 it was re-formed at RAF Station Martlesham Heath to bring the Boulton Paul Defiant fighter into service.

After initial successes, the Luftwaffe soon realised that the Defiant was vulnerable to frontal attack, and the squadron started to have heavy losses of aircraft and crew.

At the end of May 1940 the squadron was withdrawn from day fighting operations and began to train in the night fighter role.

The Mosquitos were operated as night fighters in the west of England, and on day patrols in the Bay of Biscay and western approaches.