In 1787, a Tây Sơn general, Vũ Văn Nhậm, marched north to attack the capital Thăng Long (now Hanoi).
After the fall of Thăng Long, Lê Chiêu Thống, the emperor of Lê dynasty, fled to Bảo Lộc mountain, and sent Quýnh to seek aid from the Qianlong Emperor of Qing China.
After this war, Nguyễn Huệ was recognized as the new ruler of Vietnam by Qianlong Emperor, and Lê Chiêu Thống did not manage to receive aid from Qing China any more.
Fuk'anggan, the Viceroy of Liangguang, forced Lê Chiêu Thống and his followers to cut off their hair and change to Manchurian attire.
Only Quýnh refused to do, and said: "Our heads can be cut off, but hairs cannot; skins can be flayed, but attires cannot be changed.