The A5M's most competitive adversary in the air was the Polikarpov I-16, a fast and heavily armed fighter flown by both Chinese Air Force regulars and Soviet volunteers. Air battles in 1938, especially on 18 February and 29 April, ranked among the largest air battles ever fought at the time. The battle of 29 April saw 67 Polikarpov fighters (31 I-16s and 36 I-15 bis) against 18 G3Ms escorted by 27 A5Ms. Each side claimed victory: the Chinese/Soviet side claimed 21 Japanese aircraft (11 fighters and 10 bombers) shot down with 50 Japanese airmen killed and two captured having bailed out while losing 12 aircraft and 5 pilots killed; the Japanese claimed they lost only two G3Ms and two A5Ms shot down with over 40 Chinese aircraft shot down.