Historically, several aircraft were designated bomber destroyers prior to and during the Second World War. They were a type of interceptor aircraft intended to destroy enemy bomber aircraft. Bomber destroyers were typically larger and heavier than general interceptors, designed to mount more powerful armament, and often having twin engines. They were a generally intended for day use, so were a separate category from the existing night fighters, although their characteristics overlapped heavily with night fighters, and with the concept of an interceptor in general. The United States Army Air Corps considered powerfully armed destroyers, like the Bell YFM-1 Airacuda prototype, to counter a potential attack of high-performance bombers. The Lockheed P-38 Lightning and Bell P-39 Airacobra were also initially specified to carry very heavy armament based on a central 37 mm cannon, specified as interceptor aircraft working in the anti-bomber role. Great Britain, by contrast, favored specialized "turret fighters", such as the Boulton Paul Defiant, which mounted heavy armament in a rotating turret. The P-38, a small, single-crewed example of the bomber destroyer type, was eventually outfitted with a 20 mm cannon and four.50-caliber machine guns in a central nacelle instead of a heavier cannon; it proved itself a highly competent fighter aircraft in the early phase of World War II. A deceptively similar, although completely different, designation was the GermanZerstörer. Introduced on 1 May 1939, the term did specifically exclude the defensive anti-bomber role, and envisaged a heavy fighter for offensive missions: escorting the bombers, long-range fighter suppression, and ground attack. The German designs suffered performance deficits as they were weighed down by a two- or three-man crew and extra cockpit accommodations. Since World War II, improvements in both engine power and armament generally led to a loss of interest in building bomber destroyers as a specific class of aircraft. Even small fighters were able to carry enough firepower to deal effectively with enemy bombers, and high-performance all-purpose late-war fighters—the P-51 Mustang being the prime example—excelled at all fighter roles: pursuit, bomber escort, interception, and ground attack.
