 They were expected to fight along Burma Road, conquer Yunnan and threaten Chongqing.On May 4, 1942, the Japanese army invaded Longling County, and at the same time dispatched 54 aircraft to carry out a violent bombing of Baoshan, Yunnan, the Millennium Ancient City; on the 10th, the Japanese army invaded the border city of Tengchong.At this point, a large area west of the Salween River (Nu River) fell into the hands of the Japanese army.