1st A6M5 �Zero� had been build by the Mitsubishi Jukogyo in 1943. It was developed to combat heavier built & armed Allied fighters that were knocking the sooner �Zero� out from the sky during 1943. The Nakajima NK1F Sakae 21 motor offered the airplane slightly better performance, plus the armament ended up being changed to 2- 20mm and 2- 13.2mm guns. These modifications would not make up for having less armor, or the lack of self-sealing gas tanks. However,despite these shortcomings, over 10,450 had been built, being used through the whole war because other types of Japanese aircraft continued to possess �teething� issues.
