The Battle of Xinkou () was a decisive engagement of the Taiyuan Campaign, the second of the 22 major engagements between the National Revolutionary Army and Imperial Japanese Army during the Second Sino-Japanese War. After battles at Nankou, the Chahar Expeditionary Force of the Japanese Kwangtung Army occupied Datong in Shanxi province, and began their assault on the Yenbei area. The Japanese Fifth Division started their attack from Hebei marching westwards and taking the towns of Guanglin, Linchou, Hungyuan in northwest Shanxi. 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. The Commander of the 2nd War Zone, Yan Xishan, ordered Chinese troops to retreat and set up a defense line in Niangziguan and Pingxingguan. Even after the Eighth Route Army led by Lin Biao successfully ambushed the Japanese at the Battle of Pingxingguan, the Chinese defenders suffered heavy casualties under Japanese artillery and tank assaults and were forced to retreat to Wutaishan to set up another defense line at Xinkou. 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 14th Group Army, along with Yan Xishan’s eight armies, organized a frontal defense of Xinkou, while the 18th Group Army (without the 120th division) and 101st division, 73rd division and the newly formed 2nd Division organized the defense on the right flank along the Sutou River’s south bank, commanded by Zhu De, while one division was sent to the enemy's rear to harass their left flank.