evidence: Yalu/Amnok River borders, but suggests some Chinese dissatisfaction about the status of the border with North Korea in the territory between the two rivers. [...] Rivers form the border between China and Korea, Yang appears to signal a strong continuing Chinese commitment to those river borders. From Yang's account, China's position on the stretch of territory between the Tumen/Tuman and Yalu/Amnok Rivers may be less clear. The issue is significant not for strategic reasons, but because the area in question is in the Changbai/ [...] China and Choson then made these two rivers the border between their countries is inaccurate. According to Korean sources, during the reign of King Kongmin, the Koryo government established counties and prefectures for local administration and defense structures in the Amnok (Yalu) River area so that it controlled territory south of the Amnok (Yalu) River. Later, during the reign of King Sejong in the first half of the fifteenth century, the Choson government defeated Jurchen communities and then established four counties in the Amnok (Yalu) River's upstream area and six military garrisons in the downstream area of the Tuman (Tumen) River. In this way the