The Tây Sơn wars or Tây Sơn rebellion, often known as the Vietnamese civil war of 1771–1802, were a series of military conflicts that followed the Vietnamese peasant uprising at Tây Sơn (in Central Vietnam) that were led by three brothers: Nguyễn Nhạc, Nguyễn Huệ, and Nguyễn Lữ. These revolutionary forces grew and later overthrew the ruling Vietnamese elite families and the ruling Lê dynasty. The Tây Sơn leaders installed themselves as rulers of Vietnam that held power until they were overthrown by Nguyễn Phúc Ánh, a descendant of the Nguyễn lord who was previously overthrown by the Tây Sơn. The war ended in 1802 when Nguyễn Phúc Ánh (now called Emperor Gia Long) defeated the Tây Sơn and reunited Đại Việt, then renamed the country to Vietnam.
Tây Sơn wars in the context of Gia Long
Gia Long (Chữ hán: 嘉隆) (Vietnamese: [zaː lawŋ] (North), [jaː lawŋ] (South); 8 February 1762 – 3 February 1820), born Nguyễn Phúc Ánh (阮福暎) or Nguyễn Ánh (阮暎), was the founding emperor of the Nguyễn dynasty, the last dynasty of Vietnam, which would rule the unified territories that constitute modern-day Vietnam until 1945.
A nephew of the last Nguyễn lord who ruled over south Vietnam, Nguyễn Ánh was forced into hiding in 1777 as a 15-year-old when his family was slain in the Tây Sơn revolt. After several changes of fortune in which his loyalists regained and again lost Saigon, he befriended the French Catholic Bishop Pierre Pigneau de Behaine. Pigneau championed Nguyễn Ánh's cause to regain the throne to the French government and managed to recruit volunteers however, that soon encountered difficulties. From 1789, Nguyễn Ánh was once again in the ascendancy and began his northward march to defeat the Tây Sơn, reaching the border with the Qing dynasty by 1802, which had previously been under the control of the Trịnh lords. Following their defeat, he succeeded in reuniting Vietnam after centuries of internecine feudal warfare, with a greater landmass than ever before, stretching from the Qing's borders down to the Gulf of Siam.
View the full Wikipedia page for Gia Long