Battle of Như Nguyệt River (1077) in the context of "Lý–Song War"

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.