I checked my copy of Nomonhan, Japan’s War Against Russia, 1939 by Alvin Coox, two volumes, information on the Mukden Incident in 1931 contained in volume one. The Chinese were well aware of the Japanese’s interest it taking over Manchuria, and were try to avoid giving the Japanese any pretext to launch an offensive. Part of the Chinese forces, 110,000, mentioned were actually located in North China, in the vicinity of Peking and Tientsin. The remainder were scattered across Manchuria. They did have some aircraft, but I am more than a bit dubious about the claim of tanks. If they had any, they would have been Carden-Lloye Mark VI tankettes. The Chinese put some faith in the guarantees of the League of Nations, the Kellogg-Briand Pact, and the Nine-Power Treaty governing foriegn penetration in China following WW One.