<Li> Battle of Yalu River (1904)--Russo - Japanese War </Li> <Li> Battle near to the Yalu River (1950)--Korean War </Li> <P> The Korean side of the river was heavily industrialized during the period of Japanese rule (1910--1945), and by 1945 almost 20% of Imperial Japan's total industrial output originated in Korea . During the Korean War, the movement of United Nations troops approaching the river precipitated massive Chinese intervention from around Dandong . In the course of the conflict every bridge across the river except one was destroyed . The one remaining bridge was the Sino--Korean Friendship Bridge connecting Sinuiju, North Korea to Dandong, China . During the war the valley surrounding the western end of the river also became the focal point of a series of dogfights for air superiority over North Korea, earning the nickname "MiG Alley" in reference to the MiG - 15 fighters flown by the combined North Korean, Chinese and Soviet forces . </P> <P> It was the advance of UN forces during the Korean War toward the Yalu which allowed Chairman Mao Zedong to convince his people that China needed to intervene over fears of an American invasion, since toppling communism was one of America's stated goals and Douglas MacArthur had expressed his desire to expand the war into China . </P>

When did un troops approach the yalu river