 Lê Văn Duyệt ( 1763 or 1764 – 3 July 1832 ) was a Vietnamese general who helped Nguyễn Ánh — the future Emperor Gia Long — put down the Tây Sơn rebellion , unify Vietnam and establish the Nguyễn Dynasty . After the Nguyễn came to power in 1802 , Duyệt became a high @-@ ranking mandarin , serving under the first two Nguyễn emperors Gia Long and Minh Mạng . 
