The Korean War

History - Asian Hot & Cold War (1945-90)

Why was Korea divided after WWII?

Because Japan surrendered in 1945 and the USA/USSR agreed to divide Korea at the 38th parallel: USSR occupied the North, USA the South. This created two rival states with opposing ideologies.

Why did Kim Il Sung want to invade South Korea?

To reunify Korea under communism, strengthen his political legitimacy, and exploit what he saw as South Korea’s weakness and instability.

. What international factors encouraged the North to invade?

Communist victory in China (1949), the USSR’s first atomic bomb (1949), and Stalin’s cautious approval of the invasion boosted confidence.

Why did Kim think the USA would not intervene?

Acheson’s Defensive Perimeter Speech (January 1950) excluded Korea, suggesting it was not a key US defence priority.

What was the main reason the USA intervened in Korea?

Containment: preventing the spread of communism in Asia.

How did domestic US politics influence intervention?

Truman was accused of being “soft on communism” after China’s fall in 1949; intervention protected him politically.

Why did the UN support the US-led intervention?

The USSR was boycotting the Security Council over China’s seat, so it could not veto the UN resolution.

Why was Japan important in the decision to intervene?

Japan was a key US ally and economic hub; the USA feared Korea’s fall would threaten Japan and regional stability.

Why was MacArthur significant in the Korean War?

He masterminded the Inchon Landing (Sept 1950), turning the war in the UN’s favour and retaking Seoul.

Why was MacArthur controversial?

He pushed for total victory, wanted to bomb China, criticised Truman’s limited-war policy, and acted independently of civilian authority.

Why did Truman dismiss MacArthur in 1951?

For insubordination, publicly challenging presidential policy, and risking escalation into World War III.

Why did China intervene in October 1950?

To prevent US troops reaching its border, protect the Yalu River dams, assert itself as a major communist power, and because Mao expected Soviet support.

How did China’s intervention change the war?

It reversed UN gains, forced a retreat below the 38th parallel, recaptured Seoul, and turned the conflict into a prolonged stalemate.

How did intervention affect China’s international status?

China emerged as a major global power capable of challenging the USA

What were the four phases of the Korean War?

1. North Korean invasion (June–Sept 1950)

2. UN counteroffensive & Inchon (Sept–Oct 1950)

3. Chinese intervention (Oct 1950–Jan 1951)

4. Stalemate (1951–53)

What military style characterised the later war (1951–53)?

Static trench warfare around the 38th parallel.

What was the impact of the Korean War on Korea?

Millions killed, massive destruction, permanent division of the peninsula, long-term militarisation.

What was the impact on the USA?

Massive increase in defence spending, strengthened containment policy, political controversy over MacArthur, revealed limits of US power

What was the impact on Japan?

Huge economic boost as a supply base; accelerated the “Japanese economic miracle”; strengthened relations with the USA.