Xu Shuzheng
The warlords bought machine guns and artillery from abroad, but their uneducated and illiterate soldiers could not operate or service them. A British mercenary complained in 1923 that Wu Peifu had about 45 European artillery pieces that were inoperable because they had not been properly maintained. At the , the army of Gen. Xu Shuzheng, which had seized Outer Mongolia, was attacked by a Russian-Mongol army under the command of Gen. Baron Roman von Ungern-Sternberg. The Chinese might have stopped Ungern had they been capable of firing their machine guns properly, to adjust for the inevitable upward jerk caused by the firing; they did not, and this caused the bullets to overshoot their targets. The inability to use their machine guns properly proved costly: after taking Urga in February 1921, Ungern had his Cossacks and Mongol cavalry hunt down the remnants of Xu's troops as they attempted to flee south on the road back to China.