the 27th and 29th Squadrons (Arthur Chin) from the 3rd Air Group, part of the 18th Squadron with Curtiss Hawk 75, and even the 32nd Squadron equipped with the ancient Douglas O-2MC scout/light bombers, led by former Guangxi warlord air force commander Wei Yiqing. The USSR volunteer squadrons often flew their missions together with Chinese squadrons. From the beginning of 1938 to May 1940, USSR squadrons participated in more than 50 major air battles and together with Chinese squadrons shot down 81 Japanese aircraft, damaged 114 and 14 Japanese warships. In the summer of 1940, the USSR withdrew their volunteer pilots, leaving only a small number of advisers and technical personnel in China. They continued to supply aircraft to China until June 1941 when Germany invaded the Soviet Union Curtiss Hawk 75, a new version of the Curtiss P-36 Hawk flown by Chinese pilots also took an active part in combat but did not achieve any special success. The Chinese 25th Squadron was the first unit to receive the new Hawk 75 and began to train in July 1938 under the direction of Claire Lee Chennault. On 18 August 1938, Squadron Commander Tang Pu-sheng led three Hawk 75s and 7 Polikarpov I-15s to intercept 27 Japanese planes over Hengyang; the Hawk 75s shot down one enemy plane and damaged another. Tang was shot down and killed; the other two Hawk 75s crashed during landing. The 16th Squadron of the 6th Bomber Air Group, having earlier flown the V-92 Corsair light bombers, was changed to a fighter squadron on 1 October 1938 and was sent to Zhiqiang, Hunan, to take possession of nine Hawk 75s. The pilots retrained under the direction of Chennault. At the end of the year, they were redeployed to Yibin, Sichuan, for air defense of the Chinese wartime capital of Chongqing. In January 1939, the squadron flew to Kunming, Yunnan, where it was disbanded in August the same year. Prior to 1 November 1938, the 18th Squadron was also included in the 6th Bomber Air Group, flying the Douglas O-2MC scout/light bombers; it was re-equipped with nine Hawk 75 fighters, and independently began retraining with its Squadron Commander Yang Yibai in Yibin. In January 1939 the 18th Squadron relocated to Kunming to defend the city from air attacks. On 1 August the squadron was rebased to Chongqing, and in December took part in the Battle of South