Chronology
In September 1937, Hideki Tojo sent the Japanese army stationed in Chahar to invade Shanxi in order to exploit its resources. The city of Datong fell, and the NRA was forced to go on the defensive, and concentrated their troops along the Great Wall in battles at places like Pingxingguan and to the east at in Niangziguan.
Yan Xishan also sent troops to reinforce Shijiazhuang, but that caused a lack of personnel to defend the North China area, allowing the Japanese army to break through in the north forcing the Chinese to fall back to a new line at Xinkou. Fighting continued in October in the Battle of Xinkou until the Japanese outflanked Niangziguan in late October, compromising the Chinese defense resulting in the fall of Taiyuan.
- Order of Battle Battle of Taiyuan
Read more about this topic: Battle Of Taiyuan