Brothers Nguyen Nhac, Nguyen Lu, and Nguyen Hue led the Tay Son revolution in 1771 and overthrew the Nguyen Dynasty. Thai forces were defeated by the Tay Son army in the Rach Gam-Xoai Mut front in 1785. Then, the Tay Son army marched to Dang Ngoai, and overthrew the Trinh dynasty. Le Chieu Thong, the last king of the Le Dynasty, fled to China, and asked for Qin dynasty's assistance. Nguyen Hue took the throne in Phu Xuan, now called Hue, in 1788. He led the army and marched north to defeat the Qin troop of 290,000 men in Thang Long in the first lunar month of 1789.

Quang Trung Nguyen Hue, founder of the Tay Son Dynasty, implemented progressive policies on land and education but he passed away in 1792. Nguyen Anh, supported by the French, returned to the Mekong River Delta to fight Tay Son army. Tay Son was defeated in 1802 and Nguyen Anh conquered Phu Xuan.