United Nations Counterattack

General Dean's successor, Lieutenant General Walton H. Walker, built up a strong defense in the area of Pusan, a port city on the southeastern tip of Korea. Reinforcements for his 8th Army began arriving there at a rate to permit changing a mere delaying action into a campaign to hold what was called the Pusan Perimeter, a defensive line protecting the only Korean port in UN hands. This sector was within a 140-mile (225-km) semicircular line from Pohang on the coast north of Pusan, enclosing Taegu, and running south, 50 miles (80 km) west of Pusan. The North Koreans smashed at this sector and captured Pohang. They suffered such heavy losses that for the first time the force of the invasion was blunted.

On September 15, while the main North Korean fighting force was in the southeast, General MacArthur ordered a gigantic amphibious strike at Inchon, a port on the west coast near Seoul. This bold move was a desperate gamble put into effect on extremely short notice, using troops badly needed to hold the Pusan Perimeter. Carried out by X Corps under Major General Edward M. Almond, the landings cut the supply lines of the invaders. Seoul was retaken on September 26. North Korean troops then began a general retreat north from that area and from the Pusan sector.

UN and South Korean forces then opened a drive to conquer North Korea, taking its capital, Pyongyang, on October 19. The 8th Army, operating in western Korea, moved northward toward the Yalu River at the Manchurian border. Meanwhile, X Corps made a second amphibious landing, this time at Wonsan on the east coast. The Corps captured Hamhung and Hungnam and drove north. With North Korea's army splintered, it appeared that the war would soon be over and that the UN, by virtue of occupying North Korea, could unify Korea by holding elections in the north and south.