[Why] Liao Empress Dowager Xiao and Emperor Shengzong led the main Liao force in deep southward invasion of the Northern Song, with war fire burning to the northern bank of the Yellow River at Chanzhou. The Song court was in panic and the peace faction strongly advocated moving the capital and fleeing to dodge the enemy. [What] Chancellor Kou Zhun overrode all objections and urged Emperor Zhenzong to lead the army in person. Song army morale surged, and at Chanzhou city walls a couched-bed crossbow shot dead a major Liao general. The two sides then signed at the site an equal-status peace mutual-trust agreement. [Who] Emperor Zhenzong of Song Zhao Heng under Kou Zhun's strong push showed the imperial dignity of resisting the enemy. Chancellor Kou Zhun was the strategic politician who turned the tide, and Empress Dowager Xiao was the northern woman ruler shrewd to circumstance. [How] This was the first time in Huaxia history that a Central Plains regime and a nomadic empire defined fixed boundaries and opened peaceful trade markets at an equal diplomatic level. It bought the two countries a century of peace stability and prosperity.
Why
The historic event of Treaty of Chanyuan represents a key developmental peak of the Huaxia dynastic system. The first treaty establishing equal status and trade boundaries with a northern power. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.