The Chanyuan Treaty emerged from warfare between Song and Liao, setting terms for their relationship and annual payments, and opening a long period of relative peace. Peace did not remove every friction, but diplomatic missions and border trade continued. The treaty needs to be understood through military, financial, and diplomatic arrangements together.
Historical background
The Chanyuan Treaty was signed between the Han-led Northern Song dynasty and the Khitan-led Liao dynasty in 1005, marking a pivotal point in Chinese history and in the relations between the two empires. The treaty laid the foundation for approximately a century of relative peace between the two major powers, which lasted until the Alliance Conducted at Sea was formed between the Song dynasty and the Jurchen-led Jin dynasty in the early 12th century. The diplomatic framework itself would continue to be emulated throughout East Asia until the establishment of the Mongol Empire in the 13th century.
After the Song dynasty was founded in 960, succeeding the turbulent Five Dynasties and Ten Kingdoms period, relations between Song and Liao were initially cordial. Song had more important matters on their hands, namely conquering the remaining southern states. After unifying the south in 979, Song turned their eyes north. That year, they destroyed Northern Han, a Shatuo Turk state that considered itself the legitimate successor of the Later Han dynasty that had fallen in 950. As it was under the protection of Liao, it engendered some friction between the two empires. However, what concerned Song even more was Liao's continued possession of the strategic Sixteen Prefectures, which included modern-day Beijing.
After Northern Han was destroyed by Song, Emperor Taizong decided to march on Liao holdings in the Sixteen Prefectures, but the Song forces were routed at the Battle of Gaoliang River and the emperor had to retreat in ignominy.
Song tried once again in 986, this time attempting to take advantage of the fact that a young emperor occupied the Liao throne. They advanced on the Sixteen Prefectures in three columns. However, Liao won decisive victories on all three fronts.
Liao invasion of 1004
Emperor Shengzong decided to personally launch a campaign against Song in the summer of 1004. He took cavalry and encamped about one hundred miles (160 kilometers) north of the Song capital of Bianjing (present-day Kaifeng, Henan). Reluctantly, Emperor Zhenzong marched northward to engage the Liao troops at Chan Prefecture (formerly known as Chanyuan Commandery; present-day Puyang, Henan). He decided upon this location because it was the first large settlement across from the Yellow River. The emperor believed that crossing the Yellow River would have great symbolic and psychological value.
To protect Chan Prefecture, Kou Zhun, the lead planner of the Song expedition, had implemented defensive measures such as trenches, but these defenses were already weakened after heavy fighting, resulting in many thousands of casualties, including a large number of generals. The Song court began to worry that the undertaking was not safe for the emperor because the Liao forces were making serious advances in the Hebei Circuit. However, the arrival of the emperor raised the Song troops' morale while ensuring that the subsequent battle would be important.
Significance of the treaty
Through the signing of the Chanyuan Treaty, Liao forced Song, who considered themselves the natural heirs to the central plains, to recognize them as peers.
This treaty immediately reduced the strain on Liao finances. Those annual tribute payments were used to facilitate the construction of Liao's central capital, Zhongjing (present-day Ningcheng County, Inner Mongolia). Peace with Song allowed Liao to focus more on their internal affairs and its relations with other peoples, and this new capital ultimately aided Liao in establishing an international trade network. Without the annual tribute from Song, it's highly unlikely that Liao would have been able to create such an expansive and sophisticated trade network.
This treaty also allowed Song to secure disputed territory in exchange for a minimal annual tribute. In addition, with the war over, the Song court was able to focus on other matters as well. For one, they could advance their foreign diplomacy. On a different note, they had the ability to curb military spending, which was putting serious strain on their economy. In the grand scheme of things, the annual tribute payments were a far smaller burden than Song's military spending concerning Liao.