The Korean War

Learning Objectives

  • Explain the goals of the U.S. and the United Nations during the Korean War

Concerns about Communism in Asia

A new chapter in the Cold War began on October 1, 1949, when the Chinese Communist Party (CCP) led by Mao Tse-tung declared victory against “Kuomintang” Nationalists led by the Western-backed Chiang Kai-shek. The Kuomintang retreated to the island of Taiwan and the CCP took over the mainland under the red flag of the People’s Republic of China (PRC). Coming so soon after the Soviet Union’s successful test of an atomic bomb on August 29, the “loss of China,” the world’s most populous country, contributed to a sense of panic among American foreign policymakers, whose attention began to shift from Europe to Asia.

Military Buildup

A stamp with a red-ink drawing of Joseph Stalin and Mao Zedong shaking hands.

Figure 1. The communist world system rested, in part, on the relationship between the two largest communist nations—the Soviet Union and the People’s Republic of China. This 1950 Chinese Stamp depicts Joseph Stalin shaking hands with Mao Zedong.

After Dean Acheson became Secretary of State in 1949, George Kennan was replaced in the State Department by former investment banker Paul Nitze, whose first task was to help compose, as Acheson later described in his memoir, a document designed to “bludgeon the mass mind of ‘top government’” into approving a “substantial increase” in military expenditures.

“National Security Memorandum 68: United States Objectives and Programs for National Security,” a national defense memo known as “NSC-68,” achieved its goal. Issued in April 1950, the nearly sixty-page classified memo warned of “increasingly terrifying weapons of mass destruction,” which served to remind “every individual” of “the ever-present possibility of annihilation.” It said that leaders of the USSR and its “international communist movement” sought only “to retain and solidify their absolute power.” As the central “bulwark of opposition to Soviet expansion,” America had become “the principal enemy” that “must be subverted or destroyed by one means or another.” NSC-68 urged a “rapid build-up of political, economic, and military strength” in order to “roll back the Kremlin’s drive for world domination.” Such a massive commitment of resources, amounting to more than a threefold increase in the annual defense budget, was necessary because the USSR, “unlike previous aspirants to hegemony,” was “animated by a new fanatic faith,” seeking “to impose its absolute authority over the rest of the world.” Both Kennan and Walter Lippmann were among a minority in the ‘foreign policy establishment’ who argued to no avail that such a ‘militarization of containment’ was tragically wrongheaded.

On June 25, 1950, as U.S. officials were considering the merits of NSC-68’s proposals, including “the intensification of…operations by covert means in the fields of economic…political and psychological warfare” designed to foment “unrest and revolt in…[Soviet] satellite countries,” fighting erupted in Korea between communists in the north and American-backed anti-communists in the south.

A Divided Korea

A map of North and South Korea, bordered by China to the north, the Yellow Sea to the west, the Sea of Japan to the east, and Japan to the southeast, is shown. Purple arrows show the North Korean invasion of South Korea in 1950; green arrows show the UN offensive response and the site of the landing at Inchon on September 15, 1950, and orange arrows should the Communist Chinese offensive. A dotted orange line shows the truce line of 1953. A grey dotted line shows the UN defensive line in September 1950, and a dotted green line shows the northern-most UN advance in November 1950.

Figure 2. After the initial invasion of South Korea by the North Korean People’s Democratic Army, the United Nations established a defensive line in the southern part of the country. The landing at Inchon in September reversed the tide of the war and allowed UN forces under General Douglas MacArthur to retake the city of Seoul, which had fallen to North Korean troops in the early days of the war.

After Japan surrendered in September 1945, a U.S.-Soviet joint occupation had paved the way for the division of Korea. In November 1947, the UN passed a resolution that a united government in Korea should be created but the Soviet Union refused to cooperate. Only the south held elections. The Republic of Korea (ROK), South Korea, was created three months after the election. A month later, communists in the north established the Democratic People’s Republic of Korea (DPRK). Both claimed to stand for a unified Korean peninsula. The UN recognized the ROK, but incessant armed conflict broke out between North and South.

In the spring of 1950, Stalin hesitantly endorsed North Korean leader Kim Il Sung’s plan to ‘liberate’ the South by force, a plan heavily influenced by Mao’s recent victory in China. While he did not desire a military confrontation with the U.S., Stalin thought correctly that he could encourage his Chinese comrades to support North Korea if the war turned against the DPRK.

On June 25, 1950, troops of the North Korean People’s Democratic Army crossed the thirty-eighth parallel, the border between North and South Korea. The first major test of the U.S. policy of containment in Asia had begun, for the domino theory held that a victory by North Korea might lead to further communist expansion in Asia, in the virtual backyard of the United States’ chief new ally in East Asia—Japan. The North Koreans launched a successful surprise attack and Seoul, the capital of South Korea, fell to the communists on June 28.

The United Nations (UN), which had been established in 1945, was quick to react. On June 27, the UN Security Council denounced North Korea’s actions and called upon UN members to help South Korea defeat the invading forces.  As a permanent member of the Security Council, the Soviet Union could have vetoed the action, but it had boycotted UN meetings following the awarding of China’s seat on the Security Council to Taiwan instead of to Mao Zedong’s People’s Republic of China. The UN passed resolutions demanding that North Korea cease hostilities and withdraw its armed forces to the 38th parallel and calling on member states to provide the ROK military assistance to repulse the Northern attack.

War in Korea

That July, UN forces mobilized under American General Douglass MacArthur. Troops landed at Inchon, a port city around 30 miles away from Seoul, and took the city on September 28. They then pushed north. As North Korean forces moved back across the thirty-eighth parallel, UN forces followed. MacArthur’s goal was not only to drive the North Korean army out of South Korea but to destroy communist North Korea as well. At this stage, he had the support of President Truman.

On October 1, ROK/UN forces crossed the 38th parallel, and on October 26 they reached the Yalu River, the traditional Korea-China border. They were met by 300,000 Chinese troops who broke the advance and pushed them back. On November 30, ROK/UN forces began a fevered retreat. They returned across the 38th parallel and abandoned Seoul on January 4, 1951. The United Nations forces regrouped, but the war entered into a stalemate. General MacArthur, growing impatient and wanting to eliminate the communist threat, requested authorization to use nuclear weapons against North Korea and China. Denied, MacArthur publicly denounced Truman. Truman, unwilling to threaten World War III and refusing to tolerate MacArthur’s public insubordination, dismissed the General in April. The Joint Chiefs of Staff agreed, calling the escalation MacArthur had called for “the wrong war, at the wrong place, at the wrong time, and with the wrong enemy.” Nonetheless, the public gave MacArthur a hero’s welcome in New York with the largest ticker-tape parade in the nation’s history.

On June 23, 1951, the Soviet ambassador to the UN suggested a cease-fire, which the U.S. immediately accepted. The UN forces had recovered from the setbacks earlier in the year and forced North Korean and Chinese troops back across the thirty-eighth parallel. However, combat raged on for more than two additional years. The primary source of contention was the fate of prisoners of war. The Chinese and North Koreans insisted that their prisoners be returned to them, but many of these men did not wish to be repatriated. Finally, an armistice agreement was signed on July 27, 1953. A border between North and South Korea, one quite close to the original thirty-eighth parallel line, was agreed upon. A demilitarized zone between the two nations was established, and both sides agreed to an exchange of prisoners. Five million people died in the three-year conflict. Of these, around 36,500 were U.S. soldiers; a majority were Korean civilians.

As the war wound down and the global balance of Cold War power continued to frustrate policymakers, other shifts in power occurred. General Dwight Eisenhower, the hero of the D-Day invasion, resoundingly defeated Adlai Stevenson in the 1952 presidential election, and Joseph Stalin died in March 1953.

Remembering a ‘forgotten War’

Photograph from the Korean War memorial, showing the statue of a soldier.

Figure 3. A photograph from the Korean War Veterans Memorial in Washington, D.C. The memorial includes nineteen of these larger-than-life statues, representing a platoon on patrol during the war.

Coming so soon after World War II and ending without clear victory, Korea became for many Americans a “forgotten war.” (Decades later, though, the nation’s other major intervention in Asia, the Vietnan War, would be anything but forgotten.) Perhaps indicative of the war’s marginal status when compared to World War II or Vietnam, The Korean War Veterans Memorial memorial was not dedicated until 1995. You can visit the American Battle Monuments Commission website to learn more about this memorial.

Despite it not being as well known in the nation’s collective history, it is likely one of the deadliest conflicts in East Asia and certainly one of the most destructive in Korean history. Following the desegregation of the armed services in 1948, it was also the first major conflict for the U.S. where the armed services were integrated, meaning that soldiers of all races served together.

Visit this website to read firsthand accounts of U.S. soldiers who served in Korea, including prisoners of war.

A photograph of one soldier holding and comforting another soldier.

Figure 4. With the policy of “containing” communism at home and abroad, the U.S. pressured the United Nations to support the South Koreans, ultimately supplying American troops to fight in the civil war. Though rather forgotten in the annals of American history, the Korean War caused over 30,000 American deaths and 100,000 wounded, leaving an indelible mark on those who served.

Communism in Vietnam

The Vietnam War had deep roots in the complexities of the Cold War as well as in the earlier phase of European colonialism in the nineteenth century. Vietnam had been colonized by France beginning in 1862, and was later seized by Imperial Japan during World War II. The nationalist leader Ho Chi Minh had been backed by the U.S. during his anti-Japanese insurgency and, following Japan’s surrender in 1945, “Viet Minh” nationalists, quoting Thomas Jefferson in their founding documents, declared an independent Democratic Republic of Vietnam (DRV). Yet France moved to reassert authority over its former colony in Indochina, and the United States deferred to France’s colonial imperatives, effectively sacrificing Vietnamese self-determination. Ho Chi Minh then turned to the Soviet Union for assistance in waging war against the French colonizers.

After French troops were defeated at the ‘Battle of Dien Bien Phu’ in May 1954, U.S. officials helped broker a temporary settlement that partitioned Vietnam in two, with a Soviet/Chinese-backed state in the north and an American-backed state in the south. To stifle communist expansion southward, the United States would send arms, offer military advisors, prop up corrupt politicians, prevent nationwide elections, and, eventually, send over 500,000 troops, of whom nearly 60,000 would be lost before the communists finally reunified the country.

Review Question

What was agreed to at the armistice talks between North and South Korea?

WATCH IT

This CrashCourse video explains the Cold War events in Asia and how the struggle against communist expansion led to U.S. wars in both Korea and Vietnam.

You can view the transcript for “The Cold War in Asia: Crash Course US History #38” here (opens in new window).

Try It