While the USSR provided most of the military aircraft to Chiang Kai-shek in the late 1930s, many early Chinese aircraft were supplied by the American Curtiss Aeroplane and Motor Company. In 1937 the Hawk II and Hawk III biplanes comprised the backbone of Chinese fighter aviation. These were soon followed by the Hawk 75 monoplane. The demonstration model Hawk 75N, with non-retractable landing gear was purchased in 1938 and became the personal aircraft of the American advisor to the Aviation Committee, Claire Chennault who oversaw training and lobbied for the procurement of American aircraft.