The Korean War, 1950-53

On a quiet Sunday morning in June 1950, North Korean guns opened fire. Three years later, the fighting stopped almost where it began. Yet about a million soldiers had died. This was the Cold War’s first hot war.

In this lesson, we follow Korea from a line drawn on a map to the Armistice of 1953. We see who fought, who turned the tide and why the war never ended with a peace treaty.

1Why was Korea split at the 38th parallel?

Japan ruled Korea as a colony for 35 years. That rule ended when Japan surrendered in August 1945. Korea needed a plan for the future.

The United States and the Soviet Union agreed on a quick fix. Two young American officers, Dean Rusk and Charles Bonesteel, drew a line at the 38th parallel. The Soviets took Japan’s surrender in the north. The Americans took it in the south.

The line was meant to be temporary. But the Cold War hardened it. In 1948, two rival states appeared. The Republic of Korea was set up in the south on 15 August. The Democratic People’s Republic of Korea followed in the north on 9 September.

• Japan ruled Korea for 35 years, until 1945.
• The 38th parallel was a temporary line for taking Japan’s surrender.
• Two states formed in 1948: South (15 August) and North (9 September).

2How did the war begin?

On 25 June 1950, North Korea launched a surprise invasion of the South. Its army moved fast. The UN Security Council denounced the attack and called on members to help the South.

One thing made this vote easy. The Soviet representative was absent. The Soviets were boycotting the Council, so no veto came.

A UN force took shape under American command. It drew troops from 21 countries. In 1952, the UN Command’s ground forces were about 50 percent South Korean, 40 percent American and 10 percent from other UN countries.

The early weeks went badly for the South. By early August, its army and allies held only a small corner around the port of Busan. This was the Pusan Perimeter.

• 25 June 1950: North Korea invades.
• The Soviet boycott let the UN vote pass without a veto.
• UN force: 21 countries. In 1952, ground forces were about 50% South Korean, 40% American and 10% others.
• By August, only the Pusan Perimeter held.

3How did Inchon turn the war around?

General Douglas MacArthur planned a bold stroke. He chose to land at Inchon, a port near Seoul, far behind the enemy lines. Cautious generals doubted the plan. The terrain was hard and risky.

The landing began on 15 September 1950. About 75,000 troops and 261 naval vessels took part. It cut the North Korean supply lines.

The enemy collapsed fast. UN forces recaptured Seoul about two weeks later. Then they crossed the 38th parallel and moved north. By October, they were advancing toward the Yalu River, the border with China.

• MacArthur planned the Inchon landing, 15 September 1950.
• 75,000 troops and 261 vessels.
• Seoul retaken in about two weeks. UN troops then crossed the 38th parallel.

4Why did China enter the war?

China watched the UN advance with alarm. Its leaders feared the UN troops would cross the Yalu and invade China. Peng Dehuai argued this case to Mao Zedong. The Chinese leaders agreed to intervene.

The Chinese force was called the People’s Volunteer Army. It crossed the Yalu on 19 October 1950. Peng Dehuai was its commander. The first units alone numbered about 250,000 men.

The UN forces fell back. They left North Korea in December. Seoul fell to the communist side again. Later, the UN forces fought their way back to roughly the 38th parallel.

• 19 October 1950: China’s People’s Volunteer Army crosses the Yalu.
• Commander: Peng Dehuai.
• UN forces pushed back, then settled near the 38th parallel.

5Why did the war end in an armistice, not a treaty?

After the Chinese entry, neither side could win. Talks began in July 1951. They dragged on while the fighting became a war of attrition.

The Korean Armistice Agreement was signed on 27 July 1953. The UN Command, North Korea and China signed it. It created a Demilitarized Zone four kilometres wide. A Joint Security Area at Panmunjom lets both sides meet.

South Korea’s president Syngman Rhee refused to sign it. He had wanted to unify Korea by force.

The Armistice is only a ceasefire. A final peace settlement has never been reached. So the two Koreas are still technically at war.

• 27 July 1953: Armistice signed.
• DMZ: 4 km wide. Panmunjom is the meeting point.
• No peace treaty. South Korea never signed the Armistice.

6What did the war cost?

About one million soldiers died across all sides. Civilian deaths were higher. Estimates vary widely, from more than a million to several million.

North Korea’s cities suffered terrible damage from bombing. Yet the front line ended near where it began. Three years of war moved the border very little.

• About one million military deaths.
• Civilian deaths were higher still. Estimates vary.
• The border ended near the 38th parallel.

7Why does the Korean War still matter?

People call it the Forgotten War. World War II came before it. Vietnam came after it. Both took up more space in memory.

It was still a first. It was the Cold War’s first big armed clash. It showed the pattern of a proxy war. Each superpower backed one side but avoided fighting the other head on.

Today the peninsula is still divided. The DMZ is one of the most heavily guarded borders in the world.

• The Forgotten War sits between WWII and Vietnam.
• A proxy war of the Cold War.
• Korea is still divided today.

8What are the exam traps?

• The Armistice is not a peace treaty. The two Koreas are still technically at war.
• China sent the large ground army. The Soviet Union did not send its main ground troops.
• Learn the order: invasion, Inchon, China, armistice.
• The 38th parallel was temporary in 1945. It was not planned as a border.
• MacArthur planned Inchon. Truman was the US President.