Who they were
Ly Thuong Kiet (1019-1105) was the great general-statesman of the Ly dynasty: a court eunuch who rose to supreme command of the army. He served three emperors and died in 1105 at 86.
What they did
Facing an impending Song invasion, he struck first in 1075-76, taking the border prefectures including Yongzhou, then withdrew. When the Song counter-offensive came, he met it at the Nhu Nguyet (Cau) River line in 1077; the invasion stalled there and was negotiated to an end. The four-line poem “Nam quoc son ha” - “The Southern country’s mountains and rivers are the Southern emperor’s dwelling” - is traditionally said to have been proclaimed to hearten his troops on that river; scholarship treats its authorship as anonymous, and its framing as a “first declaration of independence” is a later tradition. He also led campaigns against Champa.
Legacy
He remains the model of active defense in Vietnamese military history. Streets across Vietnam bear his name.