A. Fearing an American invasion in China, Mao Zedong dispatched troops to support North Korea's armies.
General Douglas MacArthur's landing at Inchon in September 1950 was a pivotal moment in the Korean War. This bold strategic maneuver allowed United Nations forces, led by the United States, to recapture Seoul and soon push the North Korean forces back past the 38th parallel. The advance continued toward the Yalu River, which is the border between North Korea and China. This approach to the Chinese border alarmed Mao Zedong, who feared an American invasion of Chinese territory. In response, China entered the war by sending the People's Volunteer Army into North Korea in October and November of 1950 to engage UN forces, leading to a significant escalation of the war. This intervention eventually forced MacArthur's troops to retreat from areas close to the Chinese border and altered the dynamics of the war, leading to a protracted conflict that would continue until the armistice in 1953.