First flown in April, 1939, the A6M Zero-Sen was the Allies' main opponent in the Pacific and the most famous symbol of Japanese air power during World War 2. This carrier-based fighter, designed with a low-monoplane wing and armed with a formidable array of two 20mm cannons and two 7.7mm machine guns, proved capable of handling any of the Allies' aircraft. It wasn't until the Allies studied a captured Zero that they were able to identify and exploit weaknesses such as minimal pilot and fuel tank protection. Zeros became infamous for Kamikaze attacks, in which pilots would intentionally crash explosion-laden aircraft into Allied ships.