Pusan Perimeter

Defensive cordon formed by U.S. and South Korean troops around the city of Pusan in southeastern South Korea during the early phases of the Korean War. At the end of World War II, the Korean peninsula was divided into northern and southern halves separated at the 38th parallel. North Korea was a communist dictatorship, closely aligned with the Soviet Union and communist China. South Korea was a capitalist country nominally under the protection of the United States. However, in January 1950, U.S. Secretary of State Dean Acheson excluded South Korea from the postwar defensive perimeter that the U.S. had established to prevent the spread of communism in Asia.

North Korean leader Kim Il Sung saw this as an opportunity to unite the Korean Peninsula under his rule. On June 25, 1950, the North Korean army stormed across the border and overwhelmed the poorly equipped and trained South Korean troops, who were joined by UN forces and U.S. forces hastily rushed in from Japan. The defenders were quickly pushed back into a defensive perimeter around Pusan.

Throughout August, the North Koreans launched a series of intense attacks on the Pusan perimeter. On August 4, North Korean troops crossed the Naktong River roughly 60 miles northwest of Pusan, nearly wiping out the U.S. and South Korean defenders. In an attack on August 24, the North Koreans nearly overran an American force of 20,000 men some 30 miles west of Pusan. In early September, a limited communist breakthrough 60 miles north of Pusan forced South Koreans to abandon their headquarters at Taegu. However, UN troops, reinforced by well-trained American infantry, did not break under the North Korean assault.

On September 15, 1950, an amphibious landing by U.S. and South Korean forces at Inchon Harbor relieved the siege of the Pusan perimeter. The invasion, led by U.S. general Douglas MacArthur, opened up a second front behind North Korean lines that forced the overstretched communist forces to retreat in order to avoid being encircled. The stand at Pusan was just the first act in a bitter three-year struggle. However, it demonstrated how hard the United States would fight to prevent a communist takeover of South Korea.