The Defiant night fighters had initially lacked airborne interception radar, thus enemy aircraft were spotted and attacked via the eyes of the crew alone, aided by ground-based searchlights intended to illuminate attacking bombers. In the opening months of 1941, as the German night bombing campaign reached its peak, increasing numbers of Defiant night fighter-equipped squadrons became operational and commenced night patrols although, according to Bowyers, there were relatively few claims across many Defiant sorties. As a counterpoint, aviation author John Taylor noted that during the "Blitz" on London of 1940–41, the four Defiant-equipped squadrons were responsible for shooting down more enemy aircraft than any other type in the theatre.