evidence: The origin of the friendly relations between China and North Korea, the Yalu River is a name that cannot be ignored. But in recent years, China's territory near the Yalu River has been shrinking, and North Korea's territory has been increasing accordingly. What's going on? To understand this problem, we first need to review the history of the Yalu River. Issues over the territory of the Yalu River have existed between China and North Korea since the Tang Dynasty. [...] So, why has China's territory near the Yalu River been shrinking in recent years, while North Korea's territory has been increasing? The territorial issue at the mouth of the Yalu River on the China-North Korea border has always attracted much attention. This is not only related to the political stability of the two countries, but also involves the friendship between the people. [...] However, now China has discovered that the territory at the mouth of the Yalu River on the China-North Korea border is undergoing completely different changes, which is very unfavorable to China. So, what's going on? At the mouth of the Yalu River on the border between China and North Korea, sedimentation has caused more and more sediment to be deposited in the Yalu River. This also means that small islands that originally belonged to North Korea's territory have continued to expand under the impact of sediment, thus affecting the original waterways.