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A light bomber is a relatively small and fast type of military bomber aircraft that was primarily employed before the 1950s. Such aircraft would typically not carry more than one ton of ordnance. The dedicated light bomber disappeared as fighters, due to advancements in powerplants and aircraft design, were eventually able to deliver equal or greater bomb loads while also carrying out other missions and roles.
Light bombers of World War I were typically single-engine biplanes with a bomb load of about 50–400 kg. Two of the most famous were the Airco DH.4 designed by Geoffrey de Havilland, and the Breguet 14 designed by Louis Breguet. They would often also serve as reconnaissance aircraft; examples include the Albatros C.III, Avro 504, DFW C.V, LVG C.II, Royal Aircraft Factory R.E.8, Rumpler C.I and Voisin III. The Royal Aircraft Factory B.E.2 was even modified as a pioneering night fighter in attempts to shoot down German Zeppelins.
By the 1930s air forces were seeking to replace their older biplane aircraft (for example, the RAF's Hawker Hart and VVS's Polikarpov R-5) with more modern and higher performance monoplane designs. World War II light bombers were single-engine or, less commonly, twin-engine aircraft with a bomb load of about 500–1,000 kg. Typical designs of this era were the Fairey Battle, Lockheed Hudson, Kawasaki Ki-32 (known to the Allies as "Mary"), Kawasaki Ki-48 (Allied reporting name "Lily"), Martin Baltimore, Mitsubishi Ki-30 ("Ann"), Mitsubishi Ki-51 ("Sonia"), Northrop A-17, Petlyakov Pe-2, Sukhoi Su-2 and Vultee V-11. Many of these aircraft were also used in the reconnaissance role. A few twin-engine light bomber designs were successful when converted into heavy fighters or night fighters; examples include the Bristol Blenheim and Douglas A-20 Havoc. Limited numbers of the German Dornier Do 17 and its derivative, the Do 215 were also converted to serve in the night fighter role. Light bombers were selected as a basis for night fighters during this time because early-war airborne radar systems, used to find and track targets in the dark, were bulky and often required a dedicated operator in the crew, which ruled most day fighters out of the role.
Most dive bombers were light bombers by definition, as these aircraft typically carried bomb loads of 1 ton or less. Likewise, many torpedo bombers were light bombers according to their size and warload, but unlike dive bombers it was common for these aircraft to also be used for level bombing missions; both the Japanese Nakajima B5N and American TBF Avenger saw extensive action in the light bomber role. Other designs included in the light bomber definition were ground-attack aircraft such as the Breda Ba.65 and Ilyushin Il-2 Shturmovik; later variants of the famous Junkers Ju 87 Stuka were also adapted to the ground attack role.
The light bomber, as a discrete aircraft type, began to be superseded as World War II opened. The growth of engine power from the 1,000 hp to the 2,000 hp class during the war produced single-engine fighters with greater performance, offensive and defensive capabilities than the light bombers of only a few years earlier. This gave rise to the fighter-bomber type, notably the Fw 190 F and G models, Hawker Typhoon and Republic P-47 Thunderbolt. Twin-engine, high performance aircraft with multi-role capability such as the Lockheed P-38 Lightning and de Havilland Mosquito also supplanted the older light bomber designs. By the end of the war, many of these newer planes were able to carry twice the bomb load of earlier light bombers.
Although the term is no longer widely used, the basic light bomber role remains a common one. Modern aircraft carrying out identical or similar mission profiles are generally known as attack aircraft and strike fighters.