Goryeo’s Thousand-li Wall

To guard against the Khitans and Jurchens, Goryeo built a wall a thousand li long from the mouth of the Yalu to Doryeonpo on the east coast.

Begun under King Deokjong in 1033 under the supervision of Yu So and finished under King Jeongjong in 1044, it marked Goryeo’s northern frontier. Earlier, in 1029, an outer wall had been built around Gaegyeong at Gang Gam-chan’s urging. It is distinct from the Goguryeo wall of the same name built in Liaodong against Tang.