His uncle, Sun Zhen, helped him to secure an appointment in the newly formed Whampoa Military Academy.

In 1934, Sun and Tang Enbo succeed in surrounding the Jiangxi Soviet area and cut off communists retreat route to the south and he was promoted to lieutenant general.

[1] He personally gave the order to regimental commander Xie Jinyuan to hold onto the Sihang Warehouse at the conclusion of the three-month battle.

Sun's superior, Tang Shengzhi, fled the city without giving his commanders any clear instructions on a possible breakout.

Chiang Kai-shek dispatched nine hundred men of Sun's 29th corps to the south of Chungking and they drove away the two regiments of the Japanese 3rd Infantry Division despite complete numerical and technological inferiority.

He participated early successful campaigns against the Communist forces along with his old classmates, they were Du Yuming, Fan Hanjie, Hu Lien and Liu Yuzhang.

As a seasoned veteran, he urged Du Yuming, the deputy commander of the nationalist troops to break out before it is too late.