The Mitsubishi A6M Zero was a lightweight fighter aircraft operated by the Imperial Japanese Navy Air Service (IJNAS) from 1940 to 1945. The origin of its official designation was that "A" signified a fighter and "6" for the sixth model built by Mitsubishi ("M"). The A6M was usually referred to by the Allies as the "Zero"¡ªa name that was frequently misapplied to other Japanese fighters, such as the Nakajima Ki-43¡ªas well as other codenames and nicknames, including "Zeke", "Hamp" and "Hap".
Its history mirrored that of the Empire of Japan in World War II. When it was introduced, the Zero was the best carrier-based fighter in the world and it was greatly feared by Allied pilots. The IJNAS also frequently used the type as a land-based fighter. A combination of excellent maneuverability and very long range made it one of the finest fighters of its era. In early combat operations, the Zero gained a legendary reputation, outclassing its contemporaries. Later, design weaknesses and the increasing scarcity of more powerful aircraft engines meant that the Zero became less effective against newer fighters. By 1942, due to the evolution of new tactics and techniques, Allied pilots were able to engage the Zero on more equal terms. By 1943, American and British manufacturers were producing fighters with greater firepower, armor, and speed, and approaching the Zero's maneuverability. The Mitsubishi A6M was outdated by 1944, but remained in production. During the final years of the War in the Pacific, the Zero was utilized in kamikaze operations.                                                                                                                                            -- Wikipedia