evidence: The Yalu River is a river that separates North Korea and China and has been a significant geographical marker between the two nations for centuries. It is the longest tributary of the Amur River and a major waterway in northeastern Asia. Stretching approximately 660 km in length, the Yalu traverses through both North Korea and China and is part of the border between them. In addition to its use as a natural separator, it is also a vital source of freshwater for both countries and serves as a vital trade route between the two nations. [...] The Yalu River plays an important role in the hydrology and ecology of both North Korea and China, as it is home to numerous rare species of fish, birds, and other wildlife. This makes it an important environmental resource for both countries. In recent years, changes to the river’s flow, due to both human activities and climate change, have led to increased water pollution and a decrease in the amount of water available to the ecosystem. This has had dire consequences on both the local and regional ecology, as seen in the decline of certain species of fish and birds. [...] The Yalu River serves as an important border between China and North Korea and provides both countries with an essential source of freshwater and a vital trade route. The two countries have worked together to protect the river and its resources, while also using it as a tool to promote cooperation and understanding. This river has thus become an important symbol of the two countries’ relationship and a reminder of their shared history.