The Korean War, ​1950-53​

How was Korea divided after WWII?

At the 38th Parallel; USSR occupied the North and the USA the South.

Who led North and South Korea in 1950?

North Korea: Kim Il Sung (Communist).

South Korea: Syngman Rhee (anti-Communist authoritarian).

What motivated Kim Il Sung to invade South Korea?

Desire to unify Korea under communism, belief in strong North Korean forces, and expectation of Soviet/Chinese support.

What role did the US play in the outbreak?

Ambiguity in the US "defensive perimeter" speech may have implied Korea was outside US protection.

What Cold War context encouraged the war?

Tensions after the "Loss of China" (1949), Soviet atomic bomb test (1949), and growing globalisation of Containment.

Why did Stalin support Kim Il Sung’s invasion plan?

To spread communism, test US resolve, and extend Soviet influence without direct confrontation.

What support did the USSR provide?

Weapons, training, military advisers, and approval for the invasion.

Why did Stalin avoid sending Soviet troops?

To prevent direct war with the USA and avoid provoking nuclear confrontation.

How else did the USSR influence the conflict?

Boycott of the UN allowed US-led intervention—an unintended strategic error.

What happened in the initial phase of the war (June–Sept 1950)?

North Korea swept through the South, forcing UN/US and ROK forces into the Pusan Perimeter.

What was the significance of the Inchon Landing (Sept 1950)?

A bold US amphibious assault that reversed North Korean gains and allowed recapture of Seoul.

Why did China enter the war in October 1950?

To protect its border, resist US presence near the Yalu River, and support communist allies.

How did Chinese involvement change the conflict?

Massive “human wave” attacks pushed UN forces back to the 38th Parallel.

What caused the stalemate (1951–53)?

Defensive attrition warfare, fortified lines, and reluctance of both sides to escalate further.

When was the Korean Armistice signed?

July 1953

What were the main terms of the armistice?

Ceasefire, creation of a Demilitarised Zone (DMZ) at the 38th Parallel, and no formal peace treaty.

Why was there no peace treaty?

Deep political division and unwillingness of both sides to compromise on reunification.

What delayed the armistice negotiations?

Disputes over prisoner repatriation and Stalin’s insistence on prolonging the war.

How did the war impact the Cold War globally?

It militarised the conflict and solidified the US policy of Containment worldwide.

What was the impact on US foreign policy?

Massive increase in defence spending (consistent with NSC-68), strengthening of alliances (NATO, SEATO).

How did the war affect China?

Enhanced prestige in the communist world, but caused major economic strain.

How did it affect Korea itself?

Massive casualties, destruction, and long-term division into North and South Korea.

What did the war show about the UN’s role?

Demonstrated that the UN could authorise military action, though dominated by US leadership.

What did the Korean War demonstrate about the Cold War?

It became a global conflict in which proxy wars replaced direct superpower confrontation.

What were the key turning points of the conflict?

North Korean invasion, Inchon Landing, Chinese intervention, and the stalemate.

Why was the war significant for superpower relations?

It entrenched hostility, accelerated rearmament, and formalised Cold War alliances.

How did the war shape future US actions?

Set a precedent for intervention to contain communism (e.g., in Vietnam).