Division of Korea
In 1950, North Korea invaded South Korea in order to take over all of Korea, which began the Korean War. Just before North Korea took over all of Korea, the United States sent its military to take back South Korea. After it took back South Korea, the United States tried to take over North Korea until China, North Korea's communist ally, pushed back the United States. This led to a tug-of-war that lasted throughout the war. In 1953, the fighting ended in stalemate, meaning neither side won the war, and the border was once again put on the 38th parallel, but this time it became the Korean Demilitarized Zone (DMZ).