Since the September 18 Incident in 1931, the Japanese aggressors had swallowed China's Northeast and then continued to transport troops through the pass in order to further instigate a full-scale war of aggression against China. By 1936, the Japanese army had surrounded Beiping (today's Beijing) from the east, west, and north. From June 1937, the Japanese troops stationed in Fengtai continuously held provocative military exercises...