The F4F-3 Wildcat was Grumman's first monoplane fighter and despite being outclassed by the Mitsubishi Zero, it was a surprisingly successful US Naval fighter of WWII. Although inferior to the Zero in speed, rate of climb and maneuverability, its mediocre performance was compensated by a strong structure, superior firepower, and internal protection for the pilot. The early Zeroes lacked self-sealing tanks and armor for the pilot and a few shots from the Wildcat's 0.50 caliber guns could easily bring one down. American pilots also developed tactics such as the 'Thach Weave' to minimize the advantages held by Japanese fighters.