Chosan

Ch'osan occupies the mountainous country along the Yalu River, facing the lands beyond Korea's northwestern frontier. After the region came under Koryŏ control in the late medieval period, raids continued in the early Joseon era. The government established a series of forts and stockades to defend the river country. Their sites, including Tŏngni mountain fortress and the post at Uhyŏn, recall the district's long military importance.