Initially, American postwar policy focused on Europe. But it was in Asia that the Cold War suddenly turned hot. Occupied by Japan during World War II, Korea had been divided in 1945 into Soviet and American zones. These soon evolved into two governments: communist North Korea, and anticommunist South Korea, undemocratic but aligned with the United States. In June 1950, the North Korean army invaded the south, hoping to reunify the country under communist control. North Korean soldiers soon occupied most of the peninsula. Viewing Korea as a clear test of the policy of containment, the Truman administration persuaded the United Nations Security Council to authorize the use of force to repel the invasion. (The Soviets, who could have vetoed the resolution, were boycotting Security Council meetings to protest the refusal to seat communist China.)

American troops did the bulk of the fighting on this first battlefield of the Cold War. In September 1950, General Douglas MacArthur launched a daring counterattack at Inchon, behind North Korean lines. The invading forces retreated northward, and MacArthur’s army soon occupied most of North Korea. Truman now hoped to unite Korea under a pro-American government. But in October 1950, when UN forces neared the Chinese border, hundreds of thousands of Chinese troops intervened, driving them back in bloody fighting. MacArthur demanded the right to push north again and possibly even invade China and use nuclear weapons against it. But Truman, fearing an all-out war on the Asian mainland, refused. MacArthur did not fully accept the principle of civilian control of the military. When he went public with criticism of the president, Truman removed him from command. The war then settled into a stalemate around the thirty-eighth parallel, the original boundary between the two Koreas. Not until 1953 was an armistice agreed to, essentially restoring the prewar status quo. There has never been a formal peace treaty ending the Korean War.

As this map indicates, when General Douglas MacArthur launched his surprise landing at Inchon, North Korean forces controlled nearly the entire Korean peninsula.

A photograph of a street battle in Seoul, South Korea, during the Korean War illustrates the ferocity of the fighting.

More than 33,000 Americans died in Korea. The Asian death toll reached an estimated i million Korean soldiers and 2 million civilians (many of them victims of starvation after American bombing destroyed irrigation systems essential to rice cultivation), along with hundreds of thousands of Chinese troops. Korea made it clear that the Cold War, which began in Europe, had become a global conflict.

Taken together, the events of 1947-1953 showed that the world had moved very far from the hopes for global harmony symbolized by the founding of the United Nations in 1945. No longer did the United States speak of One World (the title of Wendell Willkie’s influential wartime book). Instead, the world had been divided in two. The United States now stood as the undisputed leader of what was increasingly known as the West (although it included Japan, where permanent American military bases were established), or the Free World. NATO was soon followed by SEATO in Southeast Asia and CENTO in the Middle East, forming a web of military alliances that ringed the Soviet Union and China.

If you find an error or have any questions, please email us at Thank you!