The Korean War: Causes, Effects and The United Nations

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  • 0:02 Roots of the Korean War
  • 2:27 Korean War, 1950-53
  • 6:52 Lesson Summary
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Lesson Transcript
Instructor: Nate Sullivan

Nate Sullivan holds a M.A. in History and a M.Ed. He is an adjunct history professor, middle school history teacher, and freelance writer.

In this lesson, we will examine the Korean War. We will explore the events leading up to the war, some of its most important battles, and also highlight the key themes associated with it.

The Roots of the Korean War

To understand the roots of the Korean War, we have to go back to the end of World War II. From 1910 until the end of World War II, the Korean Peninsula belonged to the Japanese Empire. Even during World War II, the Allies were debating what should become of Korea in anticipation of victory.

In November 1943, at the Cairo Conference, U.S. President Franklin Roosevelt, British Prime Minister Winston Churchill, and Chinese Nationalist leader Chiang Kai-shek met to discuss what would become of the remains of the Japanese Empire. It was decided that the peninsula should become a free and independent country.

When the Japanese surrendered in August 1945, a provisional government was set up in Korea, with the Soviet Union exercising control over the northern half and the United States exercising control over the southern half. Remember, during World War II, the Soviet Union and the United States were allies! The boundary between the two zones of occupation was drawn at the 38th parallel, also called the Demilitarized Zone, or DMZ.

The plan was for the two halves to unite, but the United States and the Soviet Union could not agree on what type of government the new Korean nation should have. The Soviet Union wanted a communist-leaning government installed, while the U.S. wanted a democratic-leaning, pro-American government put in. Unable to reach a resolution, the Republic of Korea was declared in the southern half of the peninsula in August 1948. A month later, the Democratic People's Republic of Korea was declared in the Soviet zone of occupation.

So, there we go. We now had a North Korea and a South Korea, each state with a very different government and very different agendas. South Korea, of course, was backed by the United States and other democratic states, while North Korea was backed by the Soviet Union and communist China. You can see now how this was a recipe for disaster.

The Korean War, 1950-1953

Occasional border skirmishes throughout the late 1940s erupted into an all-out war when nearly 100,000 North Korean soldiers crossed the DMZ and attacked South Korea on June 25, 1950. You see, North Korean leader Kim Il-sung was determined to rule a united Korea. Negotiations had gone nowhere, so Sung decided to use force to achieve his aims. Armed with tanks and heavy artillery, North Korean forces advanced quickly. On June 28, the capital city of Seoul fell.

On June 27, 1950, the United Nations (UN) convened and passed Resolution 83, which authorized member states to provide military assistance to South Korea. That same day, American President Harry Truman authorized the use of United States forces to assist in the liberation of South Korea. The Korean War was not fought unilaterally between American and North Korean Forces. Rather, it was fought between United Nations forces and North Korea's Korean People's Army (KPA). That said, UN forces were predominantly composed of Americans.

One of the most important battles of the Korean War was the Battle of the Pusan Perimeter, in which United Nations forces held out for six weeks on the southeastern tip of the peninsula. It was fought throughout August and September 1950. This battle can be considered the turning point of the war. Having been pushed down the peninsula, with their backs to the sea, UN forces were successful in fending off KPA advances.

After holding out for six weeks, UN forces went on the offensive and counterattacked in the Battle of Inchon. The Battle of Inchon was an amphibious assault at the port of Inchon, which was about a hundred miles from Seoul. The battle was a decisive victory for UN forces. It resulted in the liberation of Seoul, and it pushed the KPA back up the peninsula.

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