Bắc Ninh Province in the context of "Battle of Như Nguyệt River (1077)"

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.

Cầu River (Vietnamese: Sông Cầu) is a river of northern Vietnam. It flows through the provinces/cities of Bắc Kạn, Thái Nguyên, Bắc Giang, Hanoi, Bắc Ninh. It begins at the Phia Bioóc Peak in Chợ Đồn District, west of mountainous province of Bắc Kạn.

The river has a length of 288 km and basin area of 6,030 km².

The Tày people, also known as the Thổ, T'o, Tai Tho, Ngan, Phen, Thu Lao, or Pa Di, is a Central Tai-speaking ethnic group who live in northern Vietnam. According to a 2019 census, there are 1.8 million Tày people living in Vietnam. This makes them the second largest ethnic group in Vietnam after the majority Kinh (Vietnamese) ethnic group. Most live in northern Vietnam in the Cao Bằng, Lạng Sơn, Bắc Kạn, Thái Nguyên, and Quảng Ninh provinces, along the valleys and the lower slopes of the mountains. They also live in some regions of the Bắc Ninh and Bắc Giang provinces. They inhabit fertile plains and are generally agriculturalists, mainly cultivating rice. They also cultivate maize, and sweet potato among other things.