Song–Đại Việt war

Song–Đại Việt war
Date	1075–1077
Location	Song dynasty and Đại Việt
Result	Indecisive Both sides agreed to withdraw; Captured territories held by both Song and Đại Việt were mutually exchanged in 1082, along with prisoners of war;
Belligerents
Song dynasty	Đại Việt
Commanders and leaders
Emperor Shenzong of Song; Guo Kui (郭逵); Zhao Xie (趙禼); Zhang Shoujie (張守節) †; Su Jian (蘇緘) †	Lý Nhân Tông; Lý Thường Kiệt; Nùng Tôn Đản; Thân Cảnh Phúc; Lưu Ưng Ký (POW)
Strength
Viet invasion of Guangnan West Circuit:; Battle of Yongzhou: More than 2,800 regular troops; Reinforcements: 80,000 troops; Song Counteroffensive: 50,000 soldiers; 100,000 supply train; 100,000–870,000 regular troops and people	Viet invasion of Guangnan West Circuit:; 80,000–100,000 troops; Song Counteroffensive: 60,000 (estimate)
Casualties and losses
Viet invasion:; 14th c. Vietnamese source: 100,000 killed in Guangxi; Song counterattack:; 12th c. Chinese source: 200,000 deaths; 13th c. Chinese source: 150,000 deaths; Modern sources: At least 250,000–400,000 troops and civilians (including massacre of Yongzhou): More than half of Song troops died from disease during the counteroffensive against Đại Việt	~15,000 deaths at Yongzhou

The Song–Đại Việt war, also known as the Lý-Song War, was a military conflict between the Lý dynasty of Đại Việt and the Song dynasty of China between 1075 and 1077. The war was sparked by the shifting allegiances of tribal peoples such as the Zhuang/Nùng on the frontier borderlands, and increasing state control over their administration. In 1075, Emperor Lý Nhân Tông ordered a preemptive invasion of Song dynasty territory with more than 80,000 soldiers, razing the city of Yongzhou after a 42-day siege. The Song retaliated with an army of 300,000 the following year. In 1077, Song forces nearly reached Đại Việt's capital Thăng Long before being halted by General Lý Thường Kiệt at the Như Nguyệt River in modern-day Bắc Ninh Province.

After a prolonged stalemate and high casualties on both sides, Lý Thường Kiệt offered apologies for the invasion and the Song commander Guo Kui agreed to withdraw his troops, ending the war. Further negotiations were held in the following years that consolidated the border between the two empires.