The Korean War

This section explains the causes and provides an overview of the course of the Korean War from1950-1953. The decade following World War Two saw the rapid spread of communism in the Far East. One of the most significant events was the establishment of a communist government in China in 1949, under the leadership of Mao Zedong. However, it was the conflict in Korea that became the defining crisis in the early Cold War, leading to heightened tensions between the USA and the USSR throughout the 1950s.

The success of communism in China confirmed the USA’s belief in the domino theory—the idea that if one country fell to communism, its neighbours would follow in a chain reaction. In 1950, the National Security Council (NSC-68) issued a report arguing that the policy of containment—which aimed to stop communism from spreading—was no longer sufficient. Instead, they advocated for roll back, an aggressive approach to reclaim territory that had already fallen under communist control.

Causes of the Korean War

After World War Two, Korea was liberated from Japanese rule but left divided along the 38th parallel, as part of an agreement between the Allies:

• North Korea became a Soviet-backed communist state, led by Kim Il Sung.
• South Korea was a non-communist state, supported by the USA and governed by Syngman Rhee.

Tensions between the two Koreas escalated over time, with both leaders claiming to be the rightful ruler of the entire peninsula. On 25 June 1950, with military support from China and the Soviet Union, North Korea launched a surprise invasion of South Korea, crossing the 38th parallel. This marked the start of the Korean War.

The Course of the Korean War

June 1950: North Korea’s Initial Success

The North Korean People’s Army (NKPA) advanced rapidly, using Soviet-supplied weapons and equipment. By August 1950, South Korean and American forces had been pushed back to a small defensive perimeter around the port city of Pusan.

July 1950: American and UN Involvement

• The USA’s response: Alarmed by the prospect of a communist takeover, the USA immediately deployed troops to support South Korea.
• UN intervention: The USA appealed to the United Nations, which authorised a military intervention. This decision was only possible because the Soviet Union was boycotting the UN Security Council at the time over the refusal to recognise communist China. Had the USSR been present, it would have used its veto power to block the resolution.

September 1950: UN Counterattack at Inchon

• Under the leadership of General Douglas MacArthur, UN forces staged a bold amphibious landing at Inchon, behind enemy lines. This surprise attack forced the North Koreans to retreat.
• By October 1950, UN forces had driven the North Korean army back across the 38th parallel and advanced as far as the Yalu River, on the border with China.

October 1950: Chinese Intervention

China, fearing the presence of a US-backed regime on its border, entered the war with massive reinforcements. The Chinese army, known as the People’s Volunteer Army, launched a counteroffensive, driving UN forces back below the 38th parallel. The Chinese intervention turned the tide of the war.

1951: Stalemate and MacArthur’s Dismissal

• By June 1951, the frontlines had stabilised around the 38th parallel, and the war settled into a stalemate.
• General MacArthur called for the use of atomic weapons against China, but US President Harry Truman refused, fearing it would escalate into a full-scale war with the Soviet Union. MacArthur openly criticised Truman’s decision, leading to his dismissal in April 1951.

1952-1953: Armistice Talks

• In November 1952, General Dwight D. Eisenhower won the US presidential election, promising to resolve the Korean conflict.
• On 27 July 1953, an armistice was signed at Panmunjom, restoring the border along the 38th parallel. This agreement left Korea divided much as it had been in 1950, and the division remains to this day.

Impact and Consequences of the Korean War

Cold War Dynamics

The Korean War was a major development in the Cold War because it was the first time the superpowers—the USA and the Soviet Union—engaged in a proxy war, fighting indirectly through allies. This strategy of limited war would become a defining feature of later Cold War conflicts, such as the Vietnam War.

Containment vs. Roll Back

• The war discredited the strategy of roll back, as the USA and its allies were unable to unify Korea or overthrow the communist regime in the North.
• However, the policy of containment was seen as a success, as communism had been prevented from spreading into South Korea.

US Military Presence in Asia

• Even after the armistice, the USA maintained a large military presence in South Korea, which has remained a point of tension with China and North Korea to this day.
• The establishment of the US-South Korea alliance solidified American influence in East Asia.

Human Cost

• The war resulted in an estimated 2-3 million deaths, including civilians. Both Koreas suffered massive destruction of infrastructure.
• Millions of families were divided by the 38th parallel, with no opportunity for reunification.

Broader Implications

• The war reinforced the divide between the Western bloc (led by the USA) and the Eastern bloc (led by the USSR and China).
• It prompted an arms race in East Asia and the expansion of military alliances, such as the formation of SEATO (the Southeast Asia Treaty Organisation) in 1954 to counter communist influence.

Key Dates to Remember

• 25 June 1950: North Korea invades South Korea.
• September 1950: UN counteroffensive at Inchon.
• October 1950: China enters the war.
• July 1953: Armistice signed at Panmunjom.

Revision Tip

Understanding the Korean War requires recognising its broader Cold War context:

• The Domino Theory: Why the USA believed communism had to be stopped in Asia.
• Proxy War: The Korean War as a conflict between superpowers fought through local allies.
• Containment vs. Roll Back: The war’s outcomes reinforced containment but undermined roll back.