The Messerschmitt Bf 109 was a German World War II fighter aircraft designed by Willy Messerschmitt in the early 1930s. It was one of the first true modern fighters of the era, including such features as an all-metal monocoque construction, a closed canopy, and retractable landing gear. The Bf 109 was produced in greater quantities than any other fighter aircraft in history, with a wartime production (September 1939 to May 1945) of 30,573 units. Fighter production totalled 47% of all German aircraft production, and the Bf 109 accounted for 57% of all fighter types produced. 2,193 Bf 109 A-E were built prewar, from 1936 to August 1939, with additional 1,000 or so postwar as licence built Avia S-99/S-199 and Hispano Aviación HA-1109 and HA-1112 Buchon The Bf 109 was the backbone of the Luftwaffe fighter force in World War II, although it began to be partially replaced by the Focke-Wulf Fw 190 from 1941. The Bf 109 scored more aircraft kills in World War II than any other aircraft. At various times it served as an air superiority fighter, a bomber escort, an interceptor, a ground-attack aircraft, and a reconnaissance aircraft. Although the Bf 109 had weaknesses, including a short range, and especially a sometimes difficult to handle narrow, outward-retracting undercarriage, it stayed competitive with Allied fighter aircraft until the end of the war. The Bf 109 was flown by the three top-scoring fighter aces of World War II: Erich Hartmann, the top scoring fighter ace of all time with 352 official victories, Gerhard Barkhorn with 301 victories, and Günther Rall with 275 victories. All of them flew with Jagdgeschwader 52, a unit which exclusively flew the Bf 109 and was credited with over 10,000 victories, chiefly on the Eastern Front. Hartmann refused to fly any other aircraft in combat throughout the war. Hans-Joachim Marseille, the highest scoring German ace in the North African Campaign, also scored all of his 158 official victories in the Bf 109, against Western Allied pilots. The Bf 109 was also used with good result by non-German pilots, like Finnish fighter ace Ilmari Juutilainen with 94 victories ? the highest scoring non-German fighter ace in history, Croatian fighter ace Mato Dukovac and Romanian fighter aces Alexandru ?erb?nescu and Constantin Cantacuzino.