Korean War Timeline

Japan surrenders, ending World War II. That night, U.S. Army officers Dean Rusk and Charles Bonesteel consult a National Geographic map of Asia to determine the postwar dividing line between Soviet and U.S. zones of control in Korea. Neither man is an expert on the country, and, failing to find any obvious natural barrier between the North and the South, they select the 38th parallel, a border that was tentatively proposed at the Potsdam Conference. This division places the capital city of Seoul in the American zone but just 35 miles south of the dividing line.

The Republic of Korea (South Korea) is established. Less than a month later the Democratic People’s Republic of Korea (North Korea) is established.

In a speech to the National Press Club, U.S. Secretary of State Dean Acheson outlines a U.S. Pacific defense posture that includes Japan and the Philippines but does not explicitly include Korea. In fact, he states that, “so far as the military security of other areas in the Pacific is concerned, it must be clear that no person can guarantee these areas against military attack.”

North Korean leader Kim Il-Sung proposes the “liberation” of South Korea to Soviet officials. Weeks of telegram exchanges between Beijing, Moscow, and P'yŏngyang follow, and by early spring Kim has secured assurances of support for the invasion from Soviet premier Joseph Stalin and Chinese leader Mao Zedong.

A massive artillery barrage from the North signals the beginning of the Korean War. Roughly 100,000 North Korean troops pour across the 38th parallel, and, although South Korean forces are driven back, they retire in good order.

The United Nations Security Council adopts Resolution 83, authorizing UN member states to provide military assistance to South Korea. The Soviets, who could have vetoed the resolution, are boycotting the proceedings because the Nationalist government on Taiwan still occupies China’s seat on the Security Council. Seoul falls the following day.

North Korean troops reach their farthest point of advance. Although thousands of UN troops have arrived to reinforce South Korea, months of fighting have reduced the area under their control to a 5,000-square-mile rectangle centered on the critical southeastern port of Pusan. By the time the North Korean invasion force reaches the “Pusan Perimeter,” its strength has been nearly cut in half and it is almost entirely lacking in armor.

X Corps, a force led by U.S. Maj. Gen. Edward M. Almond, stages an audacious amphibious landing at Inch’ŏn, some 150 miles behind enemy lines. The plan, conceived by UN commander Gen. Douglas MacArthur, is an unqualified success; 10 days later Seoul is liberated.

Having destroyed the bulk of the North Korean army, UN troops have pressed on into North Korea and are now approaching the Yalu River. Chinese People’s Volunteers Force (CPVF) troops under veteran commander Gen. Peng Dehuai cross into North Korea and inflict serious losses on the lead units of the UN advance. The sudden appearance of Chinese forces sends the main body of UN forces reeling back to the south bank of the Ch’ŏngch’ŏn River.

The U.S. Marines at the Chosin Reservoir begin their “attack in a different direction” as they engage in a fighting retreat to the port of Hŭngnam. Two entire Chinese armies have been tasked with the destruction of the 1st Marine Division. They succeed in driving the American force from North Korean territory but pay an enormous price: as many as 80,000 Chinese troops are killed or wounded, and the CPVF Ninth Army Group is rendered combat-ineffective for months. “Frozen Chosin” becomes one of the most-storied episodes in U.S. Marine Corps history.

Chinese and North Korean forces recapture Seoul.

Seoul changes hands for the fourth time when UN forces once again liberate the South Korean capital. The city has been devastated by fighting, and its population has been reduced to a fraction of its prewar size.

U.S. Pres. Harry S. Truman relieves MacArthur of command for insubordination and his unwillingness to prosecute a limited war. He is succeeded as UN commander by Lieut. Gen. Matthew Ridgway.

Vastly outnumbered UN forces check the Chinese advance on Seoul at the Battles of Kapyong and the Imjin River. Two Commonwealth battalions—the 2nd Battalion of the Princess Patricia’s Canadian Light Infantry Regiment and the 3rd Battalion of the Royal Australian Regiment—rebuff an entire Chinese division at Kapyong, and 4,000 men of the British 29th Brigade stage a successful delaying action against nearly 30,000 troops of the Chinese 63rd Army at the Imjin River. Some 650 men of the 1st Battalion, the Gloucestershire Regiment (the “Glorious Glosters”), engage in a Thermopylae-like stand against more than 10,000 Chinese infantry at Imjin. Although the overwhelming majority of the Glosters are killed or captured, their sacrifice allows UN forces to consolidate their lines around the South Korean capital.

Truce talks between the UN and the communists begin at Kaesŏng. The negotiations do not mark an end to the war, however; the fighting continues for two more years. In October the peace talks relocate to the village of P'anmunjŏm.

Mark W. Clark for the UN Command, Peng Dehuai for the Chinese, and Kim Il-Sung for North Korea conclude an armistice ending hostilities. A demilitarized zone is created that roughly follows the prewar border along the 38th parallel. South Korean Pres. Syngman Rhee announces his acceptance of the agreement, but no representative of South Korea ever signs the document.