allied himself with Sun and took up a post as governor of Guangdong Province under Sun, and Guo Songlian followed his mentor to Guangdong. During this period Guo served on the staff of the Guangdong, Guangxi, and Hunan Border Supervision Offices, and the head of the Guangdong Military Battalion. As a young officer, he gained the praise of Sun Yat-Sen. In May 1918, Sun Yat-Sen dissolved the Guangzhou military government under pressure from warlords, and Guo Songlian returned to Fengtian. Fengtian Clique General In 1919, Zhang Zuolin formed the Manchurian Army Military Academy 东三省陆军讲武堂, and Guo Songling was appointed as instructor in military tactics. One of his students was Zhang Zuolin's son Zhang Xueliang, who held Guo's capability in deep esteem. In 1920, Zhang Xueliang graduated from the Military Academy and was appointed a brigade commander in the Fengtian Army, and upon Zhang Xueliang's recommendation Guo was appointed to be the younger Zhang's chief of staff. As chief of staff, Guo trained the younger Zhang's brigade into one of the best brigades in the Fengtian army. In July of that year, the Zhili–Anhui War erupted, and Guo was appointed by Zhang Zuolin as commander of an allied force with the Zhili clique against the Anhui clique. Guo's forces decisively beat the Anhui forces in Tianjin, and he grew more and more in Zhang Zuolin's confidence. In 1921, Zhang Zuolin expanded the Fengtian army into ten mixed brigades, with the third directed by Zhang Xueliang and the eighth directed by Guo Songling. The third and eighth brigades formed a united command, and Guo Songling took charge of operations and training for both divisions. In May 1922, the First Zhili–Fengtian War broke out, and the Fengtian clique suffered heavy losses, but the elite third and eighth brigades were able to retreat without much casualties. Afterwards Zhang Zuolin established the Army Organizational Department 陆军整理处, with Zhang Xueliang as Chief-of-Staff and Guo Songling as Acting Chief of staff, in charge of military organization, order and training. Dissatisfaction with Zhang Zuolin and rebellion During the Second Zhili–Fengtian War a personal grievance over a friend's removal from command caused him to retreat and nearly cost his army the war. A sense that he was being under-appreciated, along with gradual encouragement by Guominjun rival Feng Yuxiang to help put Zhang's more liberal son on the Manchurian throne, led to his mutiny in mid-1925. Marching his division north