Korean War (1950-1953): The First Hot War of the Cold War

The Korean War was fought from 25 June 1950 to 27 July 1953 between North Korea, backed by China and the Soviet Union, and South Korea, supported by a United States-led United Nations Command. It was the first major armed conflict of the Cold War, swinging from one end of the peninsula to the other before settling into a costly stalemate. The armistice that ended the fighting left Korea divided, and no peace treaty has been signed since.

Background: a divided peninsula

Korea had been a Japanese colony since its annexation by Japan in 1910. When Japan surrendered in August 1945, the United States and the Soviet Union agreed to divide the peninsula temporarily at the 38th parallel to accept the surrender of Japanese forces: Soviet troops in the north, American troops in the south.

The division hardened as the Cold War developed. In 1948 two rival states were proclaimed: the Republic of Korea in the south under Syngman Rhee, and the Democratic People’s Republic of Korea in the north under Kim Il Sung. Each claimed to be the legitimate government of all Korea. Border clashes along the parallel were frequent, and both leaders spoke of unifying the country by force.

Kim Il Sung repeatedly asked Joseph Stalin for permission to invade. In early 1950 Stalin agreed, on condition that Mao Zedong, whose communists had just won the Chinese Civil War, also backed the plan. American troops had left the south in 1949, and a speech by US Secretary of State Dean Acheson in January 1950 had left Korea outside the defensive perimeter he described in the Pacific.

The North Korean invasion

Before dawn on 25 June 1950 the Korean People’s Army crossed the 38th parallel at several points. It was better equipped than the South Korean army, with Soviet-built T-34 tanks and artillery. Seoul fell on 28 June.

The United States responded quickly. The UN Security Council, which the Soviet Union was boycotting over China’s seat, passed resolutions on 25 and 27 June calling for North Korea’s withdrawal and urging members to help South Korea. President Harry S. Truman committed American air, naval and then ground forces. On 7 July the Council created a unified command under the United States, and the next day General Douglas MacArthur was named its commander.

The first American units, rushed from occupation duty in Japan, were pushed back. By August UN and South Korean forces held only a small area in the south-east around the port of Pusan (Busan). Along the Pusan Perimeter they fought off repeated North Korean attacks while reinforcements arrived.

The early weeks were also marked by atrocities against civilians. South Korean authorities executed large numbers of suspected leftists, including members of the Bodo League, in the summer of 1950, and North Korean forces killed civilians and prisoners in areas they occupied. In late July 1950 American soldiers fired on refugees at No Gun Ri, an incident that was investigated by both governments after it was reported in 1999.

Inchon and the march north

MacArthur reversed the war with an amphibious landing at Inchon, near Seoul, on 15 September 1950. The Battle of Inchon cut North Korean supply lines, and the Eighth Army broke out of the Pusan Perimeter the next day. Seoul was recaptured by the end of September, and the North Korean army collapsed in retreat.

The UN forces then crossed the 38th parallel, with UN General Assembly approval, aiming to unify Korea. South Korean troops crossed on 1 October and American forces on 7 October. Pyongyang fell on 19 October, and some units reached the Yalu River on the Chinese border.

China enters the war

China had warned that it would intervene if American forces crossed the parallel. From 19 October tens of thousands of Chinese troops, officially called the Chinese People’s Volunteers and commanded by Peng Dehuai, secretly crossed the Yalu. After a first round of clashes they launched a massive offensive in late November.

UN forces were driven back across the north. In the east, the US Marines and Army units fought their way out of encirclement in the Battle of Chosin Reservoir and were evacuated by sea from Hungnam. In the west the Eighth Army retreated south of the 38th parallel, and Seoul fell again on 4 January 1951.

Stalemate and the dismissal of MacArthur

General Matthew Ridgway took over the Eighth Army after General Walton Walker was killed in a road accident in December 1950. He restored morale and launched counter-offensives, and Seoul was retaken in March 1951, the fourth time the city had changed hands in less than a year. Chinese spring offensives in April and May 1951 were held and then pushed back at heavy cost. The front then stabilised roughly along the 38th parallel, running somewhat north of it in the east and slightly south of it in the west, where it remains today.

MacArthur publicly argued for widening the war, including attacks on China. Truman relieved him of command on 11 April 1951, a decision that caused a political storm in the United States but upheld civilian control of the military. Ridgway succeeded him.

Armistice talks began in July 1951 at Kaesong and later moved to Panmunjom. They dragged on for two years, mainly over the fate of prisoners of war: many Chinese and North Korean prisoners did not want to return home, and the UN side refused to repatriate them by force. Meanwhile bloody battles were fought over hills and ridges along the front, and American bombing devastated North Korean cities and infrastructure.

The air war introduced the first large-scale battles between jet fighters. American F-86 Sabres fought Soviet-built MiG-15s over the north-west of Korea, in an area pilots called “MiG Alley”. Many of the MiGs were flown secretly by Soviet pilots, a fact both Moscow and Washington chose not to publicise at the time. At sea, UN navies controlled the coasts throughout the war, allowing amphibious operations and the evacuation of troops and refugees.

The war also forced the major powers to consider nuclear weapons. American leaders discussed their use at several points, and Truman’s remarks at a press conference in November 1950 caused alarm in Britain and elsewhere, but no atomic weapons were used.

Key people

• Kim Il Sung, leader of North Korea, who launched the invasion.
• Syngman Rhee, president of South Korea, who opposed an armistice that left Korea divided.
• Douglas MacArthur, UN commander from July 1950 to April 1951.
• Matthew Ridgway, commander of the Eighth Army and later of all UN forces.
• Peng Dehuai, commander of the Chinese People’s Volunteers.

The armistice and the human cost

After Stalin’s death in March 1953 and the arrival of a new US president, Dwight D. Eisenhower, the negotiators reached agreement. The armistice was signed at Panmunjom on 27 July 1953. It created a Demilitarized Zone about 4 kilometres wide and some 250 kilometres long, close to the old dividing line. South Korea did not sign, and the Korean Armistice Agreement remains an armistice rather than a peace treaty.

Casualty figures are uncertain and debated. Commonly cited estimates are:

Civilians suffered terribly: from the fighting, from bombing, from cold and hunger, and from massacres committed by both sides against people suspected of supporting the enemy. Millions became refugees, and many families were permanently separated by the new border.

Legacy

South Korea, devastated in 1953, later became one of the world’s leading industrial economies and, from the late 1980s, a democracy. North Korea developed as a highly centralised state under the Kim family and later acquired nuclear weapons. The Demilitarized Zone remains one of the most heavily fortified borders on Earth, and incidents along it have periodically raised tensions.

Outside Korea, the war shaped the Cold War far beyond Asia. It confirmed American policy-makers in their commitment to containment, led to the rearmament of Western Europe and a permanent US military presence in East Asia, and pushed Washington to support the French in Indochina. War memorials in Washington, London, Ottawa, Canberra and Seoul honour those who served.

Timeline

• 1950, 25 June: North Korea invades South Korea; the UN Security Council calls for withdrawal.
• 1950, 28 June: Seoul falls to North Korean forces.
• 1950, 15 September: UN forces land at Inchon.
• 1950, 19 October: Pyongyang falls; Chinese forces begin crossing the Yalu.
• 1950, late November: China launches a major offensive.
• 1951, 4 January: Seoul is captured a second time by communist forces.
• 1951, 11 April: Truman dismisses MacArthur.
• 1951, 10 July: Armistice talks begin at Kaesong.
• 1953, 27 July: The armistice is signed at Panmunjom.

Why it matters

The Korean War fixed the division of Korea that still exists today. It also transformed the Cold War: the United States greatly increased military spending, NATO became an integrated military alliance, and China emerged as a major military power hostile to the West for a generation.