Đàng Trong
Since the 17th century Vietnam was divided into two parts: the southern part was Đàng Trong or Cochinchina, ruled by the Nguyễn lords and the northern part was Đàng Ngoài or Tonkin, ruled by the Trịnh lords under the puppet Lê emperors. In 1771 the Tây Sơn rebellion broke out in southern Vietnam, led by the brothers Nguyễn Nhạc, Nguyễn Huệ and Nguyễn Lữ, who removed the local Nguyễn lord from power.