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The Cold War (1945–1963)

History SparkNotes

The Korean War: 1950–1953

The Start of the Cold War: 1947–1952

Postwar Prosperity at Home: 1945–1960

1950 Korean War begins U.S. forces land at Inchon MacArthur retakes South Korea Chinese troops force MacArthur back to Seoul
1951 Truman fires MacArthur
1952 Dwight D. Eisenhower is elected president
1953 Korean War ends with signing of armistice
Key People
Harry S Truman -  33rd U.S. president; was commander in chief during most of Korean War
Dean Acheson -  Secretary of state during Truman’s second term; announced in 1950 that Korea was outside the U.S. defense perimeter
Douglas MacArthur -  U.S. general and commander of United Nations forces who drove North Korean forces back past the 38th parallel after making Inchon landing
Dwight D. Eisenhower -  34th U.S. president; elected in 1952 after serving as general in World War II and as supreme commander of NATO; secured cease-fire in Korea

North and South Korea

With Hitler and Mussolini defeated in Europe in 1945, the United States and Soviet Union turned to fighting Japan later in the year. After Japanese forces surrendered to General Douglas MacArthur, the United States and the USSR shared control of the neighboring Korean Peninsula, which had been under Japanese control since the turn of the century. They divided Korea at the 38th parallel, with the Soviet Union taking control in the north and the United States in the south. Both sides also armed the Koreans and erected new governments friendly to each respective superpower.

The Start of the Korean War

It seemed that Korea might become a flash point in the Cold War, but then Truman’s secretary of state, Dean Acheson, effectively announced in 1950 that the United States had no interest in Korea because it had no geopolitical significance. The Soviet Union, however, may have interpreted Acheson’s remarks as giving the USSR carte blanche regarding Korea and therefore allowed the North Korean Communist government in Pyongyang to invade South Korea in June 1950, with some Soviet support. Outnumbered and outgunned, the South Korean forces retreated to the city of Pusan on the peninsula’s southern shore. Truman watched, stunned, as the North Korean forces captured almost the entire peninsula within the span of a few months. He capitalized on the Soviet Union’s absence in the United Nations Security Council, however, to convince the other members that North Korea had been the sole aggressor. After a vote of unanimous approval, the Security Council asked all member nations to help restore peace.


Both conservative and liberal foreign policy makers in the United States viewed the North Korean invasion as evidence that the Soviet Union did in fact hope to spread Communism and as a threat to American efforts to rebuild and democratize Japan. The invasion thus made George F. Kennan’s theories about containment all the more pertinent: Truman worried that if the United States failed to act, the Soviet Union would continue to expand and threaten democracy.

In order to check this feared expansion, Truman’s new National Security Council submitted a classified document known simply as National Security Council Memorandum 68 (NSC-68), which suggested that Truman quadruple military spending for purposes of containment. The president readily consented and asked Congress for more funds and more men. Within a few years, the U.S. armed forces boasted more than 3 million men, and the United States was spending roughly 15 percent of its gross national product on the military.

The Inchon Landing

Truman made sure that General MacArthur, who had been an effective in overseeing occupied postwar Japan, was made commander of the UN forces sent to Korea. Truman then ordered MacArthur to pull U.S. troops out of Japan and retake South Korea below the 38th parallel.

In September 1950, MacArthur and his troops flanked the North Koreans by making an amphibious landing at Inchon, near Seoul. The surprise Inchon landing allowed U.S. forces to enter the peninsula quickly, without having to break through the enormous forces surrounding Pusan. Caught entirely off guard, the North Korean forces panicked and fled north, well past the 38th parallel. Truman ordered MacArthur to cross the parallel and pursue the North Koreans.

Disaster at the Yalu River

MacArthur’s crossing of the 38th parallel troubled the Soviet Union and Communist China, especially considering that Truman had entered the war vowing to restore peace and the status quo—not to conquer the entire peninsula. China therefore warned the United States not to approach the Chinese–North Korean border at the Yalu River. However, MacArthur ignored the warning and pursued the North Koreans farther up the peninsula. Interpreting this move as an act of war, the Chinese sent hundreds of thousands of soldiers across the Yalu to meet MacArthur’s men in North Korea. Overwhelmed, MacArthur and his forces retreated back to the 38th parallel.

MacArthur’s Dismissal

Stalemated once again at the 38th parallel, MacArthur pressured Truman to drop nuclear bombs on mainland China. Doing so, MacArthur reasoned, would not only allow his forces to take the entire Korean Peninsula but would also topple the Communist regime in Beijing. Truman and U.S. military officials, however, knew they lacked the resources to fight a war with China, defend Western Europe, contain the Soviet Union, occupy Japan, and hold Korea at the same time. They also wanted to keep the war limited and knew that the deployment of nuclear weapons would bring the Soviet Union into what could quickly devolve into World War III. MacArthur rebuffed these arguments and instead tried to turn the American people against Truman by criticizing him in public. Truman removed MacArthur from command in April 1951, for insubordination.

The Election of 1952

Even though MacArthur had disobeyed orders and publicly rebuked the commander-in-chief, blame fell on Truman for “losing” Korea to the Communists. Since Truman had little chance of being reelected, Democrats instead nominated Illinois governor Adlai E. Stevenson for the presidency in 1952. Republicans, meanwhile, nominated former World War II general and NATO supreme commander Dwight D. Eisenhower for president, with former Red-hunter Richard M. Nixon as his running mate. Eisenhower’s status as a war hero and Nixon’s reputation for being tough on Communists gave the Republicans an easy victory. They won the popular vote by a 7 million-vote margin and also won a landslide in the electoral college, with 442 electoral votes to Stevenson’s 89.

The End of the Korean War

By the time Eisenhower took the oath of office in 1953, American soldiers had been entrenched in Korea for nearly three years. In the time since MacArthur’s final retreat to the 38th parallel, thousands more Americans had died without any territorial loss or gain. Eisenhower eventually brought about an armistice with North Korea, in part by making it known that he, unlike Truman, would consider the use of nuclear weapons in Korea. Despite the armistice, however, the border between North and South Korea has remained one of the most heavily fortified Cold War “hot spots” in the world for more than fifty years.

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