Korean reunification selected the 38th parallel as a dividing line. Japanese troops to the North of this line were to surrender to the Soviet Union and troops to the South of this line would surrender to the United States. This was not originally intended to result in a long-lasting partition, but Cold War politics resulted in the establishment of two separate governments in the two zones in 1948 and rising tensions prevented cooperation. The desire of many Koreans for a peaceful unification was dashed when the Korean War broke out in 1950. In June 1950, troops from North Korea invaded South Korea.
Australia in the Korean War border between North Korea and China, and extend their rollback policy into China. Many in the West, including General MacArthur, thought that spreading the war to China would be necessary and that since North Korean troops were being supplied by bases in China, those supply depots should be bombed. However, Truman and the other leaders disagreed, and MacArthur was ordered to be very cautious when approaching the Chinese border. Except on some rare occasions, UN bombers remained out of Manchuria during the war. China warned American leaders through neutral diplomats that it would intervene to protect its national security, however