A civil war broke out between Nguyễn Nhạc and Nguyễn Huệ in 1787, he joined Nhạc's side. Huệ besieged Quy Nhơn, he led the main forces to support Nhạc. Getting the information, Nguyễn Ánh returned to Vietnam. Chân was defeated and captured by Huệ, and later surrendered to Huệ. After the Battle of Ngọc Hồi-Đống Đa, Huệ attempted to find a peaceful solution with Qing China. Chân was sent to China as a member of diplomatic corps.