Initial A6M5 �Zero� finished up being build by the Mitsubishi Jukogyo in 1943. It absolutely was developed to fight heavier built & armed Allied fighters which were knocking the sooner �Zero� out from the sky during 1943. The Nakajima NK1F Sakae 21 motor offered the airplane particularly better performance, and so the armament wound up being undoubtedly changed to 2- 20mm and 2- 13.2mm weapons. These improvements cannot alter having less armor, or the insufficient self-sealing fuel tanks. But,despite these shortcomings, over 10,450 is at truth built, utilized through the entire war because other forms of Japanese aircraft proceeded to acquire �teething� problems.