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In This Article Expand or collapse the "in this article" section Korean War

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Korean War by Paul M. Edwards LAST REVIEWED: 07 May 2019 LAST MODIFIED: 27 September 2017 DOI: 10.1093/obo/9780199743292-0219

The Korean War (1950–1953) was isolated between the patriotic conflict of World War II and the provocative battles of Vietnam and has been largely lost in the American memory. Yet it stands out as a significant watershed event that has left its mark on the nations involved ever since. Not only did the conflict change the nature of how wars were to be fought, but it also helped change the definition of victory. Beginning with an attack by the Democratic People’s Republic of Korea (North) on the Republic of Korea (South) in June 1950, the war dragged on for three more years and cost the lives of millions of persons. Seen by many as the first clash of the Cold War, it was nevertheless a line drawn in the sand, with the political and ideological positions of nations placing them on one side or the other. The Communist of North Korea formed a loose collaboration with Russia. The Western bloc, meanwhile, came forward to participate actually or symbolically in the conflict. Fought under the flag of the United Nations, the intention was to stop the invasion and force the withdrawal of North Korea’s forces from the South. Caught unaware and poorly prepared for another war, the United States gradually strengthened itself and halted the advance. After successfully accomplishing this mission, it was determined by the Truman administration, backed by the United Nations, that their forces should press north and put an end to the North Korea Army, in partial hopes of achieving the unification of Korea. For both military and political reasons, the Chinese intervened in October 1950, pushing the UN forces back to the south. The mobile war soon established a stalemate line near the 38th parallel, from which both sides participated in small unit engagements. After years of fruitless negotiations, a cease-fire was finally agreed to and, with the exception of South Korea, signed by the participants. The war, as well as American involvement, was never clear to the American people. Having been of minor interest during the fighting, it was generally forgotten once it was over. For nearly three-quarters of a century a cease-fire, but not an end to the war, has existed and been maintained by a combination of military threats, political diplomacy, and economic sanctions. The legacies of the war continue, and the nations are never far from war.

The fast, sporadic, and mobile character of the Korean War makes the dictionary and encyclopedia especially helpful tools, particularly for those in an introductory study. The multiple actions occurring on land, in the air, and at sea are more often organized subjectively than chronologically. Short-entry encyclopedias are also a very good source for beginning students, since each entry is generally written without reference to other topics. Most bibliographies of the Korean War are subdivided by subject. The unfortunate aspect of bibliographies is the speed at which they become dated.

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The Korean War at Sixty: New Approaches to the Study of the Korean War

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Kathryn Weathersby; The Korean War at Sixty: New Approaches to the Study of the Korean War . Journal of Cold War Studies 2015; 17 (3): 242–243. doi: https://doi.org/10.1162/JCWS_r_00574

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This fine collection of essays commemorating the 60th anniversary of the Korean War makes a significant contribution to English-language scholarship on that pivotal conflict. The authors broaden the investigation of the war by addressing new questions or bringing new perspectives to old questions about important issues of alliance diplomacy, military strategy, public opinion, and historical memory.

In “An Alliance Forged in Blood: The American Occupation of Korea, the Korean War, and the US-South Korean Alliance,” William Stueck and Boram Yi supplement the extensive scholarship on U.S. strategic calculations regarding the Korean peninsula with a subtle, balanced examination of the sources of the mutual mistrust and disrespect that quickly took root between U.S. occupiers and newly liberated Koreans. Drawing on Korean-language sources and U.S. Army documents, they chart the evolution of attitudes that contributed to Washington's failure to extend a security guarantee to the Republic of Korea (ROK)—a guarantee that might...

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The Korean War: A History

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Charles R. Kim; The Korean War: A History. Journal of Asian Studies 1 February 2012; 71 (1): 270–272. doi: https://doi.org/10.1017/S0021911811002737

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The Korean War: A History explores historical memories of the Korean War from the perspectives of the United States, North Korea, and South Korea. As the first full-length study to provide a multidimensional examination of how people in these three nation-states have remembered this pivotal mid- twentieth-century conflict, the book marks a notable contribution to the historiography of the Korean War. Author Bruce Cumings, a foremost expert on the war, brings to the table over three decades of critically minded scholarship on the historical origins and consequences of this oft-underappreciated—and still-un-resolved—war. In doing so, he compellingly argues that an earnest, reflexive reexamination by the American public of what he calls the “forgotten” and “never-known” war is long overdue (p. xv).

Deftly shuttling back and forth across the eight decades that have spanned the start of the Asia-Pacific War (1931–45) to the present, Cumings interweaves his analysis of Korean War history...

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Overview of the Korean War and its Legacy

The year 2010 marks the 60 th anniversary of the Korean War, which began on June 25, 1950. Following the three years of intensely brutal fighting and subsequent devastation, an armistice was signed on July 27, 1953. The signing of the agreement stopped the fighting and put the war on hold without a clear trajectory of future plans. To this day, the legacies of the Korean War continue to remain as a source of tension for the divided Korea as well as the regional and international community.

The Korean War is said to be a civil war between South and North Korea with its historical roots partly in the Japanese colonial experience and legacy. Under the Japanese colonial rule from 1910 to 1945, the Japanese imperial government implemented the "divide and rule" policy, which demarcated the Korean peninsula according to its geographic characteristics to utilize and exploit the natural resources more effectively. The mountainous northern part, rich with raw minerals and geographic advantages, was suited for heavy industry, while the southern part concentrated on light industry and production of rice and other crops. More importantly, this delineation coincided with the ideological division within Korea. The communist groups increasingly made their way to the north, where they engaged in guerrilla warfare as the form of resistance against the Japanese, while conservatives and collaborationist groups congregated and operated in the south. 1

At the end of World War II, when Japan surrendered to the Allies in 1945, Korea was liberated from the Japanese colonial rule only to be divided and occupied by the two major super powers of the Cold War era. The United States occupied the southern half and the Soviet Union occupied the northern half. Under the occupation rule by the two ideologically opposing foreign regimes on each side of the 38 th parallel, two separate Korean governments were formed in 1948. Backed by the United States, the government of the Republic of Korea (ROK) was headed by Syngman Rhee, while the northern government of the Democratic People's Republic of Korea (DPRK) was headed by Kim Il-sung with the support of the Soviet Union. Both Syngman Rhee and Kim Il-sung aimed to reunify Korea under their own political systems. While Rhee called for a democratic government, Kim wanted to establish a communist government for the reunified Korea. Such competing interests created tensions and mutual enmity between the South and the North and persecutions of the groups and individuals who exhibited affiliation to the opposing political system in each half of the peninsula further polarized Korea.          

Against this backdrop, numerous skirmishes in the forms of guerilla warfare and border conflict occurred between the two Koreas in the period between 1948 and 1950. 2 With the withdrawal of the occupation countries in 1949, the tensions between the South and the North continued to escalate. 3

On June 25, 1950, the Korea People's Army (KPA) of the DPRK marched southward and crossed the 38 th parallel to invade the South. In response to this northern provocation of war, the Unites States entered the war to aid the South, whose military forces were quickly subdued by their northern counterparts, to fight against the North. Secretary of State Dean Acheson's decision to intervene and to commit more military forces to the war was supported by President Truman and was later approved by the United Nations. 4 Even with the dominant numbers of US military forces on the ground, the northern army continued to successfully push southward in the summer of 1950, forcing the ROK and US armies to retreat as far as Pusan, the farthest southeastern port city on the peninsula. By early August, the northern advance was halted and the battle relatively stabilized without any party's dramatic advance through the end of the month. With the successful landing at Inchon in mid-September, the United Nations Command (UNC) forces led by General MacArthur recaptured Seoul from the KPA and Kim Il-sung's initial plan to win or "end the war in a month" then dissipated. 5

With this newly acquired momentum, the US-led UNC forces advanced past the 38 th parallel into the northern territory. Soon, the Chinese armies entered the war on behalf of DPRK in late October, namely, to defend its borders from the US-UNC advance, although the decision was determined by Chairman Mao early in the war. However, North Korean and Chinese archival documents confirm that Chairman Mao decided to intervene should DPRK face a difficult situation since Koreans sent their military troops and support for the "Chinese revolution, the anti-Japanese resistance, and the Chinese civil war." 6 Brutal fighting between the communist China-North Korea military forces and the UNC forces continued until the late spring of 1951, when the fighting stalemated in terms of the battle lines, which resembled the lines where the present-day demilitarized zone is. 7

In July 1951, truce talks began among the four belligerents (DPRK, PRC, UNC, and ROK) in the war. Another two years of negotiation and "a form of trench warfare" went on before the signing of an armistice on July 27, 1953 by three of the four main actors to the war: DPRK, PRC, and UNC. 8 South Korea's Syngman Rhee refused to sign it on the grounds that he refuses to recognize divided Korea. Nonetheless, the armistice agreement went into effect and ended the fighting and established the 2.5-mile-wide demilitarized zone (DMZ). Since this cease-fire agreement was not a peace treaty, both Koreas are still in a state of war in a technical sense.      

The tragic, destructive fratricidal war left Korea with deep scars at many levels. Sources estimate that as many as three million Koreans, at least half of which were civilians, died in the war. 9 Aside from the physical destruction of the peninsula by heavy bombings and the astronomical number of human death tolls, the war scarred the Korean psyche in that it was a conflict in which Koreans killed Koreans. The mutual animosity and fear between the South and the North continued to proliferate in the immediate postwar years as incidents of conflicts, such as border skirmishes, espionage attempts, kidnappings and the like, never ceased to arise.

The two Koreas have developed their own states under different forms of government in the postwar recovery and modernization years. South Korea has adopted democracy and capitalism while North Korea remains one of the most stringent and isolated communist states in the world today. In terms of economic development, the North was ahead of South up until 1960. However, since 1960s South Korea underwent a rapid industrialization over the course of three decades and became a competitive player in the global arena. 10 Although North Korea adheres to the "self-reliance" concept of the juche ideology, its economy is largely defunct and relies on foreign aid and alternative means to sustain the massive military regime.      

In the past decade since 2000, the two Koreas have warmed their relationship as they held the first inter-Korean summit in 2000. 11 However, more recent incidents, including the North's two missile tests in 2006 and 2009 and the resumption of nuclear proliferation, have generated concerns that attracted international community's attention and subsequently resulted in various UN sanctions imposed on North Korea. 12 13   Recognizing the threat of the North's provocations, the Six-party talks have been held to address and resolve the issues diplomatically among the key countries: North and South Korea, the United States, Russia, China, and Japan.  

Perhaps the legacy of the war is more salient on the ground level. The war created numerous war orphans and divided families in both Koreas. In South Korea, it also created US military bases, which have been present for decades, and the mandatory conscription for male citizens. The growing number of North Korean defectors also has been an increasingly frequent and telling phenomenon. These mentioned above are just a few of the legacies of the Korean War. The memory and legacy of the war is likely to continue to be indelible in the minds of Koreans in both halves of the peninsula.

• 1 Lynn, Hyung Gu. Bipolar Orders : the Two Koreas Since 1989. Halifax, NS: Fernwood Pub., 2007. p. 16.
• 2 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 146.
• 3 Cumings, B. (2010). The Korean War: A History. New York: Modern Library.
• 4 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 12-13.
• 5 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 21.
• 6 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 25.
• 7 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 30.
• 8 . Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. xviii.
• 9 Cumings, B. (2010). The Korean War: A History. New York: Modern Library. p. 35, 243.
• 10 Andrea Matles Savada and William Shaw, editors. "The Government Role in Economic Development." South Korea: A Country Study.  Washington: GPO for the Library of Congress, 1990. Available from http://countrystudies.us/south-korea/47.htm . Accessed 15 October 2010.
• 11 11. Scanlon, Charles. "Analysis: Korea summit raises hopes." BBC News. 10 April 2000.  Available from http://news.bbc.co.uk/2/hi/asia-pacific/708099.stm . Accessed 15 October 2010.
• 12 Choe, Sang-Hun and David E. Sanger. "North Koreans Launch Rocket Over the Pacific." 4 April 2009. Available from http://www.nytimes.com/2009/04/05/world/asia/05korea.html . Accessed 15 October 2010.
• 13 Neil MacFarquhar. "U.N. Security Council Pushes North Korea by Passing Sanctions." 12 June 2009.  Available from http://www.nytimes.com/2009/06/13/world/asia/13nations.html . Accessed 15 October 2010.

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What Caused the Korean War and Why Did the U.S. Get Involved?

By: Jessica Pearce Rotondi

Updated: June 26, 2023 | Original: May 7, 2021

On June 25, 1950, the Korean War (1950-1953) began when 75,000 members of the North Korean People’s Army crossed the 38th parallel and invaded South Korea. It would be the first military action of the Cold War .

In 1945, superpowers drew a line bisecting the Korean peninsula to separate the Soviet-supported Democratic People’s Republic of Korea (today’s North Korea) from the U.S.-supported Republic of Korea to the South. Essentially a civil conflict, the Korean War became a proxy war between superpowers clashing over communism and democracy. Between 2 million and 4 million people died, 70 percent of them civilians . No peace treaty was ever signed, although in December 2021, North and South Korea, the United States and China agreed to declare a formal end to the war.

What Caused the Korean War?

“The Korean War was a civil war,” says Charles Kim, Korea Foundation associate professor, Department of History, University of Wisconsin-Madison. Korea had been a unified kingdom for centuries before Japan annexed it following its victory in the Russo-Japanese War . The Japanese ruled over Korea with an iron fist from 1910 to 1945. To weaken their colony, they used assimilation tactics like forbidding the Korean language and de-emphasizing Korean history in favor of Japanese culture.

When Japan surrendered to the Allies following the dropping of atomic bombs on Hiroshima and Nagasaki during World War II, control of the Korean peninsula passed from Japan to the U.S. and the Soviet Union . The superpowers chose to divide Korea between themselves at the 38 th parallel , which roughly bisected the peninsula. “It didn’t correspond to political, cultural, or terrain boundaries,” Kim says. The Soviets set up a communist government to the North, and the United States helped establish a military government in the South.

“At the time, Korean politics ran the gamut from communism on the extreme left to right-wing nationalists, all vying for power,” Kim says. “There was a lot of contention between the Soviet and U.S. occupation forces, and with the polarization of Korean leadership, it was a volatile situation,” says Kim. “Each viewed the other as illegitimate. Both wanted to invade the other to unify Korea.”

Scattered border skirmishes from 1948-50 kept tensions simmering. In 1948, the United States called on the United Nations to sponsor a vote for Koreans to determine their future government. When the North refused to participate, the South formed its own government in Seoul under the anti-communist Syngman Rhee. In retaliation, Kim Il Sung, a former communist guerrilla, was named Premier of the Democratic People’s Republic of Korea (DPRK).

Kim Il Sung went to Moscow in 1949 and again in 1950 to seek Soviet support for invading South Korea. “He was able to get Joseph Stalin to commit to providing support for the invasion of South Korea. He also got a verbal commitment from China ,” Kim says.

When North Korea invaded South Korea on June 25, 1950, “North Korea was banking on the U.S. not coming back,” says Kim. North Korean forces were strong; they had the aid of experienced veterans of the Chinese Civil War , which had just ended in August of 1949. North Koreans made swift progress southward. The world watched to see what would happen next.

Why Did the U.S. Get Involved in the Korean War?

“The U.S. initially didn’t want to get involved in any kind of invasion. They didn’t want to get tangled up with North Korea, much less China or the Soviet Union,” says Kim. Key events on the world stage caused the United States to change course.

On August 29, 1949, the Soviets detonated their first atomic bomb. Klaus Fuchs, a physicist who had helped the United States build its atomic bomb program, had leaked the blueprint of the “ Fat Man ” atomic bomb to the Soviets. The revelation stoked Cold War paranoia. Then, on October 1, 1949, communist revolutionary Mao Zedong announced the creation of the People’s Republic of China following the defeat of the U.S.-supported Chinese nationalists led by Chiang Kai-shek. “‘The loss of China’ was a phrase used by Republican critics of the Truman administration,” says Kim.

Thousands of Chinese troops were sent to aid the North Koreans. “Mao Zedong was adamant about helping out his North Korean allies. He wanted to improve China’s prestige in the communist world by what he saw as freeing South Koreans from U.S. imperialist rule,” Kim says.

President Truman Orders US Forces to South Korea

On April 14, 1950, Truman received a document called National Security Council Paper Number 68 ( NSC-68 ). Created by the Defense Department, the State Department, the CIA , and other agencies, it advised the president to grow the defense industry to counter what these agencies saw as the threat of global communism. The recommendations cemented Truman’s next move.

On June 27, 1950 , President Truman ordered U.S. forces to South Korea to repulse the North’s invasion. “Democrats needed to look tough on communism,” Kim says. “Truman used Korea to send a message that the U.S. will contain communism and come to the aid of their allies.”

The United States never formally declared war on North Korea. Instead, Truman referred to the addition of ground troops as a “police action.” U.S. General Douglas MacArthur ’s Inch’on landing on September 8, 1950, turned the tide of the war and enabled Southern forces to push Northward beyond the 38 th parallel.

On December 16, 1950, U.S. President Harry Truman declared a state of emergency , proclaiming that “communist imperialism” was a threat to democracy. 

Impact of the Korean War

The Korean War armistice , signed on July 27, 1953, drew a new border between North Korea and South Korea , granting South Korea some additional territory and demilitarizing the zone between the two nations. A formal peace treaty was never signed.

Over 2.5 million people died in the Korean War. Despite two prisoner-of-war exchanges , Operation Little Switch and Operation Big Switch, 7,800 Americans are still missing in action, while South Korea is still searching for over 124,000 servicemen .

“The absence of a final conclusion to the Korean War has kept it alive as a major influence on Asian affairs,” says Sheila Miyoshi Jager, professor of East Asian Studies at Oberlin and author of Brothers at War: The Unending Conflict in Korea . 

She argues the Korean War directly influenced President Lyndon B. Johnson’s policy in Vietnam : “Here was a successful sovereign nation, divided by the Cold War, being threatened by its communist neighbor backed by China and the Soviet Union. Korea was now seen as a war that had successfully stopped the Chinese communist expansion in Asia.”

Sandwiched between World War II and the Vietnam War, the Korean War was nicknamed “The Forgotten War.” But to Jager, it’s not over: “The Korean War continues to influence events in East Asia,” she says. Tensions between the United States and North Korea remain.

HISTORY Vault: Korea: The Forgotten War

Five years after WWII, America is once again plunged into bloody battle. Robert Stack hosts this penetrating documentary about the war in Korea.

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