The state-of-the-art new Japanese Mitsubishi A6M "Zero" fighters were first deployed into combat in course of the Chongqing and Chengdu bombing raids, and received its first baptism of fire in aerial combat on 13 September 1940; 13 Zeroes of the 12th Kokutai led by Lieutenant Saburo Shindo which had escorted 27 G3M bombers on a raid into Chongqing were sent against 34 Chinese fighters: including Polikarpov I-15bis (led by Maj. Louie Yim-qun of the 28th PS) and I-16 (led by Capt. Yang Mengjing of the 24th PS) and other Polikarpov fighters of Maj. Zheng Shaoyu's 4th PG. The battle lasted about half an hour by which point the Chinese were low on fuel and had to break off; with some luck, escaping further contact with the much faster Zeroes. Many of the Polikarpovs were damaged or shot down (the Zero pilots claiming 27 Polikarpovs shot down), with ten pilots killed in action, and eight wounded, Maj. Zheng and Lt. Gao Youxin managed to drive Zeroes off the tails of other Chinese fighters, with Lt. Gao closing-in to 50 meters (160 ft) of one, and claiming a Zero shot-down, but in fact only four Zeroes suffered some damage, and all 13 safely returned to base in Wuhan.