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.
United States in the Korean War were destroyed. The US had lost the battle, revealing that the mere sight of US troops would not reverse the military balance in Korea. By early August, the North Korean troops had pushed back the US and South Korean troops all the way to Naktong River, which is located about thirty miles from Pusan. The two weeks of fighting following this resulted in the most casualties of US troops than any other equivalent period of this war. However, during this time the US pushed supplies and personnel to Korea and by the end of July South Koreans and US troops