The Mitsubishi A6M Zero was a long-range fighter aircraft of Imperial Japan, manufactured by Mitsubishi Heavy Industries, and operated by the Imperial Japanese Navy from 1940 to 194?. The A6M was designated as the Mitsubishi Navy Type 0 Carrier Fighter (Japanese: 零式艦上戦闘機 Rei-shiki-kanjō-sentōki), and also designated as the "Mitsubishi A6M Rei-sen" and "Mitsubishi Navy 12-shi Carrier Fighter". The A6M was usually referred to by its pilots as the "Zero-sen", zero being the last digit of the Imperial year 2600 (1940) when it entered service with the Imperial Navy.
When it was introduced early in World War II, the Zero was considered the most capable carrier-based fighter in the world, combining excellent maneuverability and very long range. In early combat operations, the Zero gained a legendary reputation as a dogfighter, achieving the outstanding kill ratio of 12 to 1, but by mid-1942 a combination of new tactics and the introduction of better equipment enabled the Allied pilots to engage the Zero on generally equal terms. A successor airplane, the Mitsubishi A7M, entered service in 1945 but production was disrupted by an earthquake in Nagoya and by Allied bombing and never became widespread.
The Imperial Japanese Navy Air Service ("IJNAS") also frequently used the type as a land-based fighter. By 1943, inherent design weaknesses and the failure to develop more powerful aircraft engines meant that the Zero became less effective against newer enemy fighters, which possessed greater firepower, armor, and speed, and approached the Zero's maneuverability. Although the Mitsubishi A6M was outdated by 1944, design delays and production difficulties of newer Japanese aircraft types meant that it continued to serve in a front line role until the end of the war. During the final years of the War in the Pacific, the Zero was also adapted for use in kamikaze operations. During the course of the war, Japan produced more Zeros than any other model aircraft.