Battle of the Như Nguyệt River

Under the first Lý kings the power of Thăng Long spread among the chieftains of the uplands along the Chinese frontier, and the Song court abandoned its long policy of avoiding trouble in the south. K. W. Taylor links the war closely with the reform policies of Wang Anshi, who encouraged activist officials on the border to prepare for war. Late in 1075 Lý Thường Kiệt struck first: a land and sea force of eighty to a hundred thousand men took the Song ports at modern Qinzhou and Hepu, destroyed the Song fleet assembled there and early in 1076, after a siege of forty-two days, took and destroyed Nanning, killing tens of thousands of people. Proclamations posted by his soldiers accused the Song of sheltering rebels and preparing an attack, and claimed that the Viets had come to rescue the people from Wang Anshi’s new laws.

The Song expedition under Guo Kui and Zhao Xie, around 50,000 soldiers with more than twice as many porters, crossed the border near the end of the lunar year and reached the Cầu River, some 45 km north-east of Thăng Long. On the southern bank Lý Thường Kiệt had built many layers of bamboo fences and assembled over four hundred war boats, and the Song army, without naval support, stalled on the northern bank. Several hundred Song soldiers crossed on floating bridges and were killed or captured; a night attack by Lý Thường Kiệt across the river was beaten back — a Viet general was captured and two Lý princes drowned. After more than a month, with over half of their army dead from battle, heat and fevers and the rains approaching, the Song generals accepted a conciliatory message from the young king Lý Càn Đức as a submission and withdrew.

Fighting in the uplands of Lạng Sơn and Cao Bằng went on for some months; in 1079 the two courts reached a settlement, and in 1088 a border agreement drew a line that, with minor changes, Taylor describes as basically the present frontier. Later historians attributed to Lý Thường Kiệt the poem ‘Mountains and Rivers of the Southern Country’, said to have been sung in temples on the southern bank during the battle; Taylor doubts that he wrote it, though he finds the story of chanting in temples plausible. The Đại Việt sử ký toàn thư tells under 1076 that one night the soldiers heard the verses recited in the temple of the deified generals Trương Hống and Trương Hát, while the Lĩnh Nam chích quái connects a version of the poem with the war of 981. Taylor’s account places the battle in the first months of 1077; some accounts give 18 January to 28 February.