 In course of the Warlord Rebellion in northeastern Shandong of 1929, Sun and 7,000 soldiers under his command joined the insurgents against the Nationalist-aligned ruler of eastern Shandong, Liu Zhennian.In 1930, he fought with warlords Feng Yuxiang and Yan Xishan in the Central Plains War against Chiang Kai-shek's government.Sun's forces were involved in a major friendly fire incident during this war, as they mistakenly fired on Feng's troops at Shangqiu.