Chanyuan Treaty: peace between the Song and the Liao

After its founding in 960 the Song tried to win back the Sixteen Prefectures around present-day Beijing, held by the Khitans since 938, but its offensives of 979 and 986 ended in defeat. From 999 the Liao, governed in practice by Empress Dowager Xiao (Chengtian) on behalf of her son Shengzong, attacked the Song frontier every year, and in the autumn of 1004 the emperor and his mother marched south in person. Failing to take Yingzhou, the Khitan army pressed on to Chanzhou, whose northern and southern towns faced each other across the Yellow River, linked by a floating bridge. Urged on by the councillor Kou Zhun, the reluctant Zhenzong led his army north and on 9 January 1005 crossed to the northern town; the sight of the imperial banner on its gate tower is said to have raised the troops' spirits. Shortly before, the Liao vanguard commander Xiao Talin had been killed by a bolt from a heavy frame-mounted crossbow — on 5 January according to the History of Liao, on 7 January according to Li Tao's chronicle of the Northern Song.

Peace feelers had been put out through Wang Jizhong, a Song general captured in 1003 who had won the trust of the Empress Dowager. The envoy Cao Liyong travelled between the camps; the Liao demanded the lands south of the frontier passes, which the Song refused, offering money instead. According to Li Tao, Zhenzong allowed Cao to promise as much as a million if he had to, while Kou Zhun threatened to have him beheaded if he agreed to more than 300,000; when Cao returned and held three fingers to his cheek, a palace eunuch took this to mean three million and the emperor cried out ‘Too much!’ — until Cao named the real figure of 300,000. The Song emperor's sworn letter, dated 19 January 1005, promised 200,000 bolts of silk and 100,000 taels of silver every year, to be delivered at the border town of Xiongzhou; each side was to keep its borders, not harbour the other's fugitives or disturb its fields, and repair existing walls and moats but build no new fortifications or canals. The Liao emperor answered with the same oath on 24 January. Zhenzong addressed Shengzong as his younger brother and the Empress Dowager as his aunt.

Many Song officials resented the payments, but they cost far less than war, and the Liao used the income in part to build a new Central Capital, begun in 1007. In 1042, while the Song was at war with the Western Xia, the Liao threatened to attack and obtained an increase of 100,000 bolts and 100,000 taels a year. The peace held until the Song allied with the Jurchens against the Liao in the early 12th century. Historians stress that the treaty treated the two emperors as equals — for the first time each side accepted the other's ruler as a Son of Heaven — and the treaty became the model for Song relations with the Western Xia and the Jin.