The Cold War in Asia: Korea and Vietnam

History · A Level: The globalisation of the Cold War, 1950-1975 (exams to Nov 2026). The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

In June 1950 communist North Korea invaded the South. Truman saw this as a test of containment, so the USA led a UN force to defend South Korea. The UN drove north, China then entered the war, and the fighting ended in 1953 with Korea still divided.

In Vietnam the USA backed the South after the French left in 1954. Leaders feared the domino theory: if one state fell, its neighbours would follow. Involvement grew from advisers to over 500,000 troops.

The USA could not defeat guerrilla forces, and opinion at home turned against the war. Nixon withdrew US troops through Vietnamisation, and the North took the South in 1975.

Rules to remember

25 June 1950: North Korea, led by Kim Il Sung, invaded South Korea across the 38th parallel.
The UN Security Council backed action because the USSR was boycotting it and could not use its veto.
September 1950: MacArthur's landing at Inchon; late 1950: China intervened as UN forces neared the Yalu River.
July 1953: armistice at Panmunjom, with Korea divided close to the 38th parallel.
1954: French defeat at Dien Bien Phu; Geneva Accords divided Vietnam at the 17th parallel.
August 1964: Gulf of Tonkin Resolution; January 1968: Tet Offensive; January 1973: Paris Peace Accords.
April 1975: Saigon fell and all of Vietnam came under communist rule.

Common mistake

Students mix up the two dividing lines. Korea was divided at the 38th parallel and Vietnam at the 17th parallel. Also remember that Korea ended in an armistice, not a peace treaty or a victory.

Worked example

Why did Truman treat the invasion of South Korea as a matter for the USA, even though Korea was far from Europe?

China had become communist in 1949, so communism seemed to be advancing across Asia.
Truman believed the attack had Soviet backing and was a test of the policy of containment.
If the USA did nothing, allies such as Japan might doubt US promises of protection.

Answer: He saw it as a test of containment: failing to act would encourage further communist expansion and weaken trust in the USA.

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