The Mitsubishi A6M5c Type 52 "Zero" was an upgraded version of the Zero fighter developed in an attempt to close the performance gap between the new American fighters such as the Hellcat and Corsair. The aircraft had a 15mph increase in top speed over the earlier version plus improvements in armor and armament. Over 6,000 of the Type 52 Zero were produced in the closing 2 years of the war when the aircraft was the Japanese Navy's primary fighter.