Yalu River, a river of Asia, which rises on the eastern borders of China and flows southwestward and southward, forming during its entire course a part of the boundary between China and Korea. Its length is about 300 miles, and it is navigable for about 30 miles. At the mouth of this river a famous naval battle was fought in 1894, during which the Japanese destroyed the Chinese fleet. The forcing of the passage of this river at its mouth by the Japanese in 1904 was the first movement in the land operations of the Russo-Japanese War. See RUSSO-JAPANESE WAR.