The Dewoitine D.520 is a French fighter aircraft that entered service in early 1940, shortly after the beginning of the Second World War. The D.520 was designed in response to a 1936 requirement from the French Air Force for a fast, modern fighter with a good climbing speed and an armament centred on a 20 mm cannon. At the time the most powerful V-12 liquid-cooled engine available in France was the Hispano-Suiza 12Y, which was less powerful, but lighter than contemporary engines such as the Rolls-Royce Merlin and Daimler-Benz DB 601.
Other fighters were designed to meet the specifications but none of them entered service, or entered service in small numbers, too late to play a significant role during the Battle of France. Unlike the Morane-Saulnier M.S.406, which was at that time the most numerous fighter in the French Air Force, the Dewoitine D.520 came close to being a match for the latest German types, such as the Messerschmitt Bf 109.
It was slower than the Bf 109E but superior in manoeuvrability. Because of production delays, only a small number were available for combat against the Luftwaffe. The D.520 proved to be relatively capable as a dogfighter against the Luftwaffe's inventory, but lacked sufficient numbers to make a difference. Following the armistice of 1940, the D.520 continued to be used, being operated by both the Free French Air Force and the Vichy French Air Force.
