1940 battle of the Second Sino-Japanese War
The Battle of Wuyuan (March 16 – April 3, 1940; ) was a Chinese counterattack that defeated the Japanese invasion of the Wuyuan area. This happened in reaction to the Chinese 1939-40 Winter Offensive in Suiyuan during the Second Sino-Japanese War. The Japanese call it 第２次後套作戦 ("The Second Battle of Wuyuan").
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.
Units.
Japanese Forces:
Mongolia Garrison Army 駐蒙軍 - Naosaburo Okabe
Chinese Forces:
8th War Area - Deputy Commander Fu Zuoyi
Course of the battle.
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. The Japanese garrison retreated northward. Chinese forces then moved on to capture a strongpoint around Hsin-an-chen on the 22nd. This cut the road along the Yellow River to Wuyuan.
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 north of Wuyuan. For three days they fought the 101st Division without success. By the 25th they had been reinforced to 3,000 men and made the crossing with artillery and air support. Wuyuan again fell to the Japanese on the 26th and the Chinese fell back to the banks of Fang-chi-chu and continued their attacks at Xin'an, Xishanzui, Xixiaozhao, and Man-ko-su.
The "Middlesboro Daily News" which reported on Japan's planned offensive into the Muslim region, predicted that the Japanese would suffer a massive crushing defeat at the hands of the Muslims.
Muslim Generals Ma Hongkui and Ma Hongbin defended west Suiyuan, especially Wuyuan in 1940 against the Japanese. Ma Hongbin commanded the Muslim 81st corps and incurred heavy casualties, but after fierce fighting eventually repulsed the Japanese and defeated them. 
Unable to withstand the pressure of Chinese attacks, the Japanese at Wuyuan retreated on March 30 and 31. On April 1 a guerrilla force and cavalry column recaptured Wuyuan, and the 11th Provisional Division recaptured Wu-pu-lang-kou. On April 3, cavalry recovered Xishanzui as the Japanese retreated to the east.
Japan used poison gas against the Chinese armies at the Battle of Wuyuan and Battle of West Suiyuan.
Sources.
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