During the evacuation of the British Expeditionary Force from Dunkirk, the squadron was based at RAF Manston, as one of the 16 squadrons that No. 11 Group had for the evacuation. On 27 May 264 Squadron claimed three He 111 and two damaged. On 28 May, shortly after take-off, 10 Defiants were attacked by about 30 Bf 109s – forming a circle, they claimed six German fighters for the loss of three Defiants. The Defiant was initially successful against enemy aircraft and its best day was 29 May, when No. 264 Squadron claimed 37 kills in two sorties: 19 Ju 87 "Stuka"s, mostly picked off as they came out of their dives, nine Messerschmitt Bf 110 twin-engined heavy fighters, eight Bf 109s, and a Ju-88; one Defiant gunner was lost after he bailed out, although the aircraft made it back to its base to be repaired. On 31 May, seven Defiants were lost in one day.