 Joining Wang Jingwei's Reorganized National Government of the Republic of China, he was given command of Collaborationist Chinese Army's 6th Group Army District which guarded the southern Beijing–Hankou railway, and was made a member of its National Military Council.In August 1943 his troops were defeated by PLA forces in the Linnan Campaign.When the Second Sino-Japanese War was over, Sun participated in the Chinese Civil War on the side of the Nationalists.