Shi Yousan

In 1912, Shi switched allegiance to Feng Yuxiang and gradually rose through his ranks.

In October 1924, Feng launched the Beijing Coup and subsequently established the Guominjun. Shi became one of the "thirteen guardians/protectors"(十三太保) considered the most important commanders of the Guominjun. Shi became the commander of the 8th Mixed Brigade of the 1st Army. In 1925, he was promoted to the commander of the 6th Division.

In 1926 during the Anti-Fengtian War, Shi's troops were stationed at Nankou (Now Changping, Beijing). Yan Xishan attacked the rear of the Guominjun from Shanxi. and Shi, along with Han Fuju's forces were sent to fight against Yan's army. Due to the inferiority of the their strength, they were forced to abandon Nankou in August of the same year, the main force of Feng subsequently retreated from Beijing. Abandoned by the main force, Shi and Han decided to surrender to Yan.

In July of the same year, Chiang Kai-Shek launched the Northern Expedition. In September Feng swore allegiance to Chiang and the Kuomintang. Shi returned to Feng's forces, and was appointed as the commander-in-chief of the 5th division of the Guominjun Army in Shaanxi. In June of the following year, the Guominjun was reorganized into the 2nd Army Group of the National Revolutionary Army, and Shi became the deputy commander-in-chief of the 1st Front Army and the commander of the 5th Army. Subsequently, Shi defeated Sun Chuanfang's forces loyal to the Beiyang government in Shandong. During the second phase of the Northern Expedition, areas controlled by the National Revolutionary Army in Henan Province was attacked and captured by the forces of Fan Zhongxiu. Feng ordered Shi's troops to move south from Shandong to engage in battle with Fan's forces along with the forces of Song Zheyuan.

By the end of 1928, the Northern Expedition was declared over, and with the demobilization, Shi was reassigned to the of commander of the 24th Division of the National Revolutionary Army and was stationed at Nanyang.