The A6M entered service in 1940 and became known as the Zero because of the Japanese designation of Type 0 Carrier Fighter. The Zero technology was years ahead of any other fighter and had no problem clearing the skies of opposing aircraft. There were numerous variants of the Zero including the folding wing A6M2 Model 21 designed for carrier operations. The A6M2 was the most produced Japanese aircraft of WWII. As the war went on the Model 21 would be the Zero variant that most Allied pilots would encounter.
Sakai became a pilot in 1937. In 1938 Sakai flew an A5M Navy Type 96 fighter, scoring one victory over a DB-3 bomber. In 1940 he was chosen to test the new A6M Zero against the Chinese and in late 1941 joined the Tainan Air Group on Taiwan. He used A6M2 Zero V-173 while based on Rabaul in June and July 1942. Ordered to shoot down any Allied aircraft, military or civil Sakai refused to shoot down a C-47 when he saw a woman and a child onboard. Sakai is credited with 64 victories.