By 1940, it was clear to both the RAF and the "Luftwaffe" that the deadliest opponents of bombers were single-engine, single-seat fighters with fixed, forward firing armament. Apart from the extra weight and drag imposed by the four-gun turret and second crew member, the Defiant lacked any directly forward-firing armament. Should the gunner need to escape from the turret in an emergency, the only way he could do this was to traverse the turret to one side and bail out through the escape hatch — but if the aircraft's electric system was disabled, immobilizing the all-electric turret due to its power source being knocked out, there was no escape. After the strong intervention of Dowding, who realised the Defiant was designed to an unworkable concept, there were only two units equipped with this aircraft, 141 and 264 squadrons. On 19 July, after encountering Bf 109s of III./JG 51, 141 Sqn had four Defiants shot down, one written off and one damaged, with 10 crew members killed or missing. Just over a month later, on 24 August 264 Sqn suffered the loss of four Defiants shot down and three badly damaged with seven crew members killed. Both units were withdrawn from 11 Group, reequipped, and took no further part in daytime operations. However, the Defiant was found to be more effective as a night fighter. It equipped four squadrons and during the winter "Blitz" on London of 1940–41, Defiants shot down more enemy aircraft than any other type.