After battles at Nankou, the Chahar Expeditionary Force of the Japanese Kwantung Army occupied Datong in Shanxi province, and began their assault on the Yenbei area.

[3] By late September, the Japanese commander Itagaki Seishiro ordered the fifth division and the Chahar Expeditionary Force to begin attacking the Chinese defense line along the inner Great Wall in Shanxi.

[3] The Commander of the 2nd War Zone, Yan Xishan, ordered Chinese troops to retreat and set up a defense line in Niangziguan and Pingxingguan.

[3] Yan Xishan gathered all available Chinese troops under his command to make a stand at Xinkou because the location was flanked by Wutaishan and Yunzhonshan, which was favorable for the defenders and was a gateway to Taiyuan, the capital of Shanxi.

On October 1, the Japanese central command ordered Itagaki Seishiro to lead the Fifth Division and Chahar Expeditionary Force for the final assault on Taiyuan.

On the same day, the military commission of the Chinese Nationalist government ordered the 14th Group Army (commanded by Wei Lihuang) to fight the Japanese at Xinkou.

The 5th Divisions used 30+ airplanes, 40+ heavy artilleries, 50+ tanks to flank the infantry's assault; while the Chinese central defense forces used the favorable terrain to put up stiff resistances despite a lack of firepower.

During this time, the Communists’ Eighth Route Army executed several guerrilla attacks in the Japanese troops rear at Lingqiu, Guangling, Weixian, Pingxingguan, Ningwu and Yanmenguan.

Although the Chinese defenders fought bravely on a united front against the enemy during this campaign, they had a large shortage of firepower, especially with the ill-equipped 8th route army.