According to S.L.A. Marshall, Brigadier General U.S. Army Res. Ret. in work entitled "The Military History of the Korean War", he quotes Admiral Matthias Gardner of the U.S. as pointing to the 38th parallel, which crosses Korea in the middle, and he asked: 'Why not put the dividing line there?' Few words have led to more vast consequences."
The Counterattack of the United States and United Nations by Douglas MacArthur
The North Korean forces draw the South Koreans into the area of Pusan, a port city on the southeast of Korea. There was a stronghold for the United Nations forces called "the Pusan Perimeter". The North Koreans smashed at this section and later, captured Pohang. The South Koreans suffered huge losses for the first time. The force of the invasion was devastating. Then, on September 15, General MacArthur ordered a strike at Inchon, a port on the west coast near Seoul, ruining the supply routes to the Communist invaders. South Korean capital, Seoul was recaptured on September 26. North Korean troops then began a general retreat north from that area and from the Pusan Perimeter. UN and South Korean forces then opened an invasion to conquer North Korea, taking its capital, Pyongyang, on October 19. The 8th Army Intelligence, operating in western Korea, moved northward toward the Yalu River at the Manchurian border. Meanwhile, X Corps made a second amphibious landing at Wonsan on the east coast. The X Corps captured Hamhung and Hungnam and drove north. With North Korea's army dissolving, it appeared that the war will soon be over and that the UN, by virtue of occupying North Korea, could unify Korea by holding elections for the two nations.