Yalu or Amnok river in eastern Asia, forming most of the boundary between North Korea and China. About 790 km (490 mi) long, it rises on the southern slopes of the Changbai Shan mountains, flows in a generally southern and southwestern direction, and empties into Korea Bay, an arm of the Yellow Sea, just south of Andong (An-tung), China. Among its tributaries are the Hun, Changjin, and Tongno rivers. Navigable only by small craft for most of its length, the Yalu is important as a source of hydroelectric power and as a waterway for the logging industry. Among the Korean cities on its banks are Sinŭiju, its port Yongamp’o, and Hyesan. The Yalu figured prominently in the fighting during the First Sino-Japanese War (1894-1895), the Russo-Japanese War, and the Korean War.