The early Northern Song regime had actively intended to conquer Vietnam for annexation when Le Hoan (黎桓) established the Tien Le dynasty (前黎朝), Song dispatched troops to go to war. It decisively revealed Song’s intention to annex Vietnam. but after a miserable defeat, Song could not help but accept the reality and was consistent in carrying out a policy to maintain friendly relations with Vietnam until the reigns of emperors of Zhenzong (眞宗) and Renzong (仁宗).
Due to this principle, there were few military conflicts between Song and Vietnam until the reign of Taizong (太宗). But after late 1040, the rebellion of the Nong clan (?氏), who resided in Qua?ng Nguyen (廣源), came to be a pending issue between the two sides. As the Ly dynasty (李朝) of Vietnam intensified pressure on and control over the Nong clan, the Nong clan rose in revolt. This rebellion exerted a strong influence on the Song dynasty. To cope with Nong’s rebellion, Song adopted countermeasures by careful consideration of relations with Vietnam. In 1053, the Nong rebellion was suppressed by Di Qing (狄靑), who was dispatched by Song.
Song’s appeasement policy toward Vietnam was changed by the accession of Shenzong (神宗) and Wang Anshi (王安石). After 1073, Northern Song sent Shen Qi (沈起) and Liu Yi (劉彛) to Guangxi to put military pressure on Vietnam. As Song was preparing for war against Vietnam, Vietnam felt a threat of invasion and launched a preemptive attack on Song in the eleventh month of 1075. As Qinzhou (欽州), Lanzhou (廉州) were captured and Yongzhou (邕州) devastated by Vietnam, Song immediately entered into a state of war and organized expeditionary forces. In the tenth month of 1076, Song’s military forces entered into Vietnam. Song’s military arrived at the Phu Lu River (富良江) on the twenty first day of the twelfth month, and fought Vietnam’s army. Directly after this combat, Vietnam asked for terms of peace and with their acceptance by Song, the war came to an end. The terms of peace which was suggested by Vietnam was the “cession of five states: To-mau (蘇茂), Tu-lang (思琅), Mon (門), Lang (諒), and Qu?ng-Nguyen” in the borderland. In fact, Song could not help but withdraw under unavoidable circumstances, and also could not achieve the intended goal.
The Song dynasty set to govern the newly acquired territory, but these five states were located in the southern border area, too far away from central districts. Thus it was very difficult for Song to settle in unaccustomed climate and foreign customs. Further, after 1077, Vietnam intermittently aggressed upon these territory to recover their territory. In January 1078, the Ly dynasty sent an envoy to Song, and demanded the return of the territory. It was a heavy burden for Song to govern these regions, and Song could not continue to possess these five states. Finally, Song dynasty returned the territory to Vietnam in 1079.