Seo Hui’s Negotiation

During the first Khitan invasion Seo Hui negotiated with the enemy commander Xiao Sunning, securing the Khitan withdrawal and the six garrisons east of the Yalu.

Xiao Sunning claimed that Goryeo had arisen from Silla land and that the old Goguryeo territory belonged to the Khitans, demanding land and a break with Song. Seo Hui replied: "Our country is the successor of Goguryeo; that is why it is called Goryeo and keeps Pyongyang as a capital. By that measure, even your Eastern Capital is our land." Relations were impossible, he said, only because Jurchens on the Yalu blocked the way; if they were driven out and the land given to Goryeo, ties would follow.

The Khitans agreed, and Goryeo founded six garrisons east of the Yalu — Heunghwajin, Yongju, Tongju, Cheolju, Gwiju and Gwakju — in exchange for breaking with Song and using the Liao calendar. It is praised as diplomacy that read the Khitans’ real aim of securing their flank before confronting Song.