||The Boulton Paul Defiant was an attempt to combine the performance of a monoplane fighter with the flexibility and concentrated firepower of turret-mounted guns; it failed miserably. The weight of the turret and a two-man crew greatly impeded the Defiant's performance, and it had no ability to fire forward, which left it with a number of blind spots in its defence.
The first Defiants entered service with Britain's Royal Air Force in December 1939 and their early operations saw vastly different outcomes. The first operational Defiant mission in May 1940 resulted in the loss of five of the six aircraft employed, but another in the same month claimed the destruction of 18 German aircraft, surprised by the turret armament, without loss. German pilots, however, soon learned of the Defiant's inability to fire forward. Losses mounted and the Defiant was withdrawn from daylight operations in August 1940.
It was given a second chance as a night-fighter and performed much more capably, particularly when equipped with airborne intercept radar. For a time Defiants had the greatest kill-per-intercept ratio of any RAF night-fighter. By 1942 the Defiant was being relegated to secondary roles, such as a target towing, air-sea rescue, radar calibration, electronic countermeasures, and training. A total of 1,075 Defiants were built before production ended in 1943.