The I-15, I-16 and I-153 fighters were the world's first mass-produced fighters. A total of 17,000 Polikarpov fighters had been manufactured by the time their series production was terminated in 1941. Aircraft of the first series successfully operated in Spain with the Republicans during the civil war (1936-39), in Chinese hands against the Japanese (1937-38), and then with the Soviet Red Air Force again against the Japanese in Mongolia during the Nomonhan Incident (1939). Russian-flown fighter also saw action against the Finns in 1939-40 during the Winter War.

By the time the...