What impact did China make when entering the Korean War against the US?
By November of 1950, UN troops under Douglas Macarthur had driven the North Koreans out of the South and all the way back to the Yalu River, the North Korean border with China. At this point, China decided to act, sending hundreds of thousands of troops into North Korea to stop Macarthur's advance. The UN troops were forced to rapidly withdraw with great loss of life, and fell back behind the 38th parallel, the border between North and South Korea. By the following summer, the two sides had settled into a stalemate, and Macarthur, who had publicly criticized President Harry Truman's decision not to expand the war by bombing sites within China, was removed from command. An armistice was signed in 1953 that solidified the 38th parallel as the permanent border, creating a demilitarized zone around it that still exists today. So the impact of China's entry into the war was essentially to preserve North Korea as a nation, and to drive UN forces back into South Korea, leading to a stalemate.