“Korean Amnok River River between NE China and N. Korea. Some 491 mi (790. Km) long, it rises on the N border of N. Korea, then flows to Korea Bay. It is an important source of hydroelectric power and is navigable by smaller vessels for most of its course. It became a political boundary in the 14th cent. During the Korean War, as U.N. forces battled toward it in 1950, Chinese troops crossed it, in effect marking their entry into the war.”
Excerpted from: Stevens, Mark A., Ed. Merriam Webster’s Collegiate Encyclopedia. Springfield, Massachusetts: Merriam-Webster, 2000.