By 28 January 1940 the Japanese had built up forces from the 26th Division at Baotou sufficient to launch the 第1次後套作戦 or "First battle of Wuyuan in Inner Mongolia" to recover lost territory and move west to take Wuyuan which fell on February 3 and Linhe further west on 4 February.
Japanese Forces: Mongolia Garrison Army 駐蒙軍 - Naosaburo Okabe Chinese Forces: 8th War Area - Deputy Commander Fu Zuoyi On March 16, 1940, as the Japanese were attacking the New 4th Division west of Linhe, the rest of the Chinese 35th Corps with the New 31st Division and a regiment of the Garrison Brigade, secretly moved east along the Wu-chia River.
On the night of the 20th they entered Wuyuan by surprise and after a seesaw fight over the strongpoint captured the city at 1600 hours on the 21st.
In an attempt to recover the situation the Japanese sent 600 troops from Dashetai via Siyitang in 80 trucks to make a forced crossing of the Wu-chia River at Ta-tsai-chu 10 km (6.2 mi) north of Wuyuan.
Ma Hongbin commanded the Muslim 81st corps and incurred heavy casualties, but after fierce fighting eventually repulsed the Japanese and defeated them.