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The Korean War

By Gregg Brazinsky

The Korean War was a complex and multifaceted event that played a determining role in the evolution of the Cold War in Asia.

Table of Contents


The Korean War was a complex and multifaceted event that played a determining role in the evolution of the Cold War in Asia. For many years, history textbooks misunderstood the origins and nature of this conflict. They began their coverage of the war with the events of June, 1950 when North Korea (also called the Democratic People’s Republic of Korea or DPRK) launched a full scale invasion of South Korea (also called the Republic of Korea or ROK). They did not pay as much attention to the conditions that prevailed on the Korean peninsula during the years between 1945 and 1950. Any effort to fully understand the nature and impact of the Korean War must begin in 1945 when a nation rife with unresolved civil conflicts was divided by the world’s two new superpowers - the United States and the Soviet Union. The conflicting agendas pursued by Americans, Soviets and different groups of Koreans during the subsequent five years made the peninsula ripe for war by 1950.

Korea in 1945

In 1945 Korea was a nation with deep political, social and economic divisions. Many of these divisions had been created during the previous thirty-five years when the country had been colonized and governed by Japan. The dawn of the twentieth century, found Japan determined to emulate the Great Powers of Europe by creating its own empire. The Japanese had long maintained that they had a special interest in Korea because of its geographical proximity. With much of the rest of the world already carved up by Europe and the United States, Japan annexed Korea in 1910. For Koreans who had been slowly awakening to the need to reform their government and strengthen their nation against foreign influence, Japan’s annexation of their homeland was a tragedy.

Japanese imperialism had created new opportunities for Koreans who were willing to collaborate. The imperial government had sought to accelerate the processes of economic growth and industrialization on the Korean peninsula in ways that would strengthen Japan. In this context, a small number of wealthy Korean landlords who were able to invest their profits into industry and commerce benefitted greatly. Japan also needed Koreans who could serve as judges, administrators, and police in its colonial system. With few other life chances available, some Koreans made pragmatic decisions to assume these roles. While some Koreans benefited from collaboration, those who resisted suffered. This was especially true during the years between 1938 and 1945 when Japan mobilized Korean society to support its involvement in World War II. Hundreds of thousands of Korean peasants were forced to labor in war related industries, including 1.4 million Koreans who were drafted and assigned to work in Japanese mines and factories. Somewhere between 100,000 and 200,000 Korean women were forced into sexual slavery as “comfort women” for the Japanese military.

When Japan surrendered its empire at the end of World War II, the Koreans who had born the heaviest burdens during the Japanese colonial period naturally looked to create a more equitable socio-economic order. The majority of Koreans were in favor of dramatic change. They wanted land to be seized from large land-holders and redistributed to the peasants. They wanted an eight-hour work day and they wanted a new more democratic government that would enable both men and women to vote. But Korean landlords, merchants and other Koreans who had cooperated with the Japanese were opposed to this kind of social change. As soon as the Japanese left the peninsula both proponents and opponents of these changes formed their own political parties and began to compete for the right to govern their newly liberated nation.

Initially, leftists who supported land reforms and improved working conditions seemed to be gaining the upper hand. When the Japanese surrendered they appointed a man by the name of Yŏ Ŭn-hyŏng as Korea’s interim president. The Japanese appeared to have chosen Yŏ because he had genuine nationalist credentials that could earn him the support of the majority of the Korean people but at the same time promised not to exact revenge on Japanese colonial administrators, who needed to remain in Korea for a short time before they could be returned safely to their native country. In the brief period of time after Japan surrendered, Yŏ began the task of setting up a new government on the Korean peninsula. He managed to create a government that possessed a surprising degree of legitimacy and popularity. A new organization known as the Committee for the Preparation of Korean Independence (CPKI) was established Seoul, the traditional capitol. In September 1945, the CPKI convened a nationwide people’s assembly. At this assembly, several hundred representatives from around the country announced the formation of a new Korean government that would be known as the Korean People’s Republic (KPR). Upon its formation, the KPR put forward a twenty-seven point platform that included sweeping land reform and many of the other items that Korean leftists had longed to see implemented. Although the KPR made an effort to include Korean conservatives, the radical nature of its programs and the potential implications for such programs on wealthy Korean landlords and businessmen assured that opposition to the KPR would emerge. The most significant opponent of the KPR was the Korean Democratic Party (KDP).

The KDP has sometimes been accused of being a stronghold for wealthy Korean landlords and businessmen who had collaborated with Japanese colonialism and it is true that the party has some figures with histories of collaboration. At the same time, the KDP also included some genuinely conservative nationalists who did not have such histories. It attracted some who wanted to see social change occur in post-war Korea but preferred that it occur gradually. By the time American and Soviet forces occupied the Korean peninsula in 1945, the KDP and the KPR were already competing for influence and power.

The Occupation of the Korean Peninsula

At the Potsdam conference in July 1945, Washington and Moscow agreed that when the Soviet armed forces entered the war against Japan the following month, they would be responsible for all ground actions in Korea. However, as the Japanese Army collapsed with unexpected speed following the Soviet entry into the war on August 9, the U.S. government became worried that Soviet control over Korea would endanger its position in Japan. Consequently, late at night on August 10, the Americans hastily drafted a proposal to divide the Korean peninsula into two zones for the purpose of accepting the Japanese surrender. Much to the Americans’ surprise, the Soviet leader Joseph Stalin accepted this proposal. He ordered Soviet forces to stop at the 38th parallel, the dividing line the Americans had proposed. A month later, American troops arrived to take up positions in the South. For Koreans, the division and occupation of their homeland was completely unjustified, as they were a liberated people, not a former enemy. The line of division, the 38th parallel, had no logic and no historical or geographical significance. It had been chosen by the Americans simply because it would place the Korean capitol Seoul in the US occupation zone.

Although they possessed almost no understanding of the conditions that existed in Korea, General John R. Hodge and other American officers in charge of the occupation were suspicious of the indigenous KPR because they had received reports that it was backed by the Soviet Union. General Hodge and American occupation forces not only refused to recognize the KPR, but were unwilling to meet with its elected leaders. Washington subsequently decided to establish a military government in the southern zone. The occupation did fill many of the administrative positions in the new military government with Koreans but the vast majority were conservatives who had been affiliated with the KDP.

In the following months, American occupying forces endeavored to seek out political leaders in Korea that would vigorously oppose Communist influence and support the establishment of a democratic government. Unfortunately, few liberal democrats of the type that Americans were looking for existed in Korea. During the period between the fall of 1945 and the spring of 1947 the U.S. Military Government made several failed attempts to create Korean councils or committees that could prepare Korea for the creation of an independent government. The problem for the United States was that for such nascent political institutions to acquire popular legitimacy, they needed to make an effort to include leftists who remained popular. At the same time, however, the United States worried that allowing leftists to influence these committees would enable Communists to gain control over all of Korea. As a result American policy attempted to allow some leftists to be fairly elected to these councils while trying to ensure that conservatives maintained the upper hand. Ultimately, however, the conflicts between left and right proved irreconcilable and every American effort to create a preparatory political institution failed.

In this context, Syngman Rhee swiftly rose to political prominence in the American occupied zone. Rhee had spent most of the previous four decades in the United States attempting to lead an international movement for Korean independence. Rhee’s politics were staunchly right wing and when the military government authorized his return to Korea, Rhee immediately aligned himself with the KDP. Americans had no illusions about the nature of his leadership. Nevertheless, Rhee was tolerable to Americans because he was staunchly anti-Communist. The fact that he had remained in exile during the colonial period and campaigned for national independence gave him a genuine nationalist credential and a degree of prestige among his fellow Koreans that other Korean conservatives lacked. As American efforts to find more moderate leaders foundered, Rhee bided his time and looked for issues that could strengthen his popular support.

In the meantime, events in the Soviet occupied north were taking a very different direction. The Soviets sought to ensure that the political system they put in place would be friendly and enable them to benefit from Korean industrial resources. But because the left was already predominant in Korean politics, they found assuring the emergence of friendly political leaders relatively easy. The Soviets did not eliminate the People’s Committees as the Americans did in the south, but instead reorganized these organizations to increase the representation of communists. They also quickly established a centralized administration for their zone, staffed with Koreans and supervised by Soviet officials, who had the ultimate authority. To head the new government for their zone, the Soviets selected a young guerilla fighter, Kim Il Sung, who had taken refuge in the Soviet Union during the war. By February of 1946, Kim had consolidated his position as the most powerful Korean political figure in the north. By the fall of 1946, he had created the North Korean Workers’ Party (NKWP), a powerful new political organization that he used to eliminate rival parties.

Initially, neither the United States nor the Soviet Union had intended the division of the Korean peninsula to result in the establishment of separate states. At the Yalta conference of February 1945, Stalin had accepted Roosevelt’s proposal to place Korea under trusteeship for several years while a permanent government was created. At the Moscow conference of December 1945 the United States, Great Britain and the Soviet Union reached an agreement on Korean trusteeship whereby a U.S.-Soviet Joint Commission would convene the following spring to create a single provisional government for the whole country. But the sharp ideological differences between the Korean political leaders that emerged in the northern and southern zones combined with the irreconcilable differences between Americans and Soviets made it impossible for the Joint Commission to reach agreement. In response, in September 1947 the United States turned to the United Nations to create a government for Korea. The United Nations Temporary Committee on Korea (UNTCOK) was created and assigned the task of supervising elections for the entire Korean peninsula. When the Soviets and the nascent Korean regime in the north refused to allow UNTCOK access to their zone, the United States persuaded the U.N. to support separate elections in the south. The Republic of Korea (ROK) was formally inaugurated in Seoul in August 1948 while the creation of the Democratic People’s Republic of Korea (DPRK) in the north was declared three weeks later. Syngman Rhee became the first President of the Republic of Korea and Kim Il Sung became Premier in the DPRK.

The Outbreak of the Korean War

The two new Korean states were hostile toward each other from the time that they were created. The political leaders of the two new states viewed each other as illegitimate and representative of ideas that they had struggled to oppose since the Japanese colonial period. Although a full-scale war did not break out on the Korean peninsula until June 25, 1950, the two states swiftly began taking some of the steps that would lead to it. Armies had begun to develop on both sides of the thirty-eighth parallel even before separate states were established. The United States had helped to create a “constabulary” in the south in December, 1945. After 1948 this constabulary became the basis of the ROK Army. Once the Republic of Korea was inaugurated the Army rapidly enlisted thousands of new recruits so that it had nearly 100,000 men by the time the war broke out. The United States continued to play a powerful role in training and equipping this new army. It not only sent material support but also deployed military advisors who helped to train the army.

Kim Il Sung had begun creating his own military in 1946. He appointed his close political allies to the highest ranking military posts. Much as the United States supplied equipment and advice to the ROK military, the Soviet Union supplied weapons and guidance to the military in North Korea. Soviet military advisors remained on the Korean peninsula after the DPRK was formally inaugurated in 1948, while some of the DPRK’s military leaders traveled to the Soviet Union for training. Within months both Koreas had significant armies and conflict between the two was starting to appear more and more likely.

A number of small-scale armed conflicts erupted during the spring of 1949. Particularly fierce battles occurred in May 1949 near at the border city of Kaesŏng and in August 1949, when DPRK forces attacked ROK Army units occupying a small mountain north of the thirty-eight parallel. During the first conflict at Kaesŏng, 400 North Korean and 22 South Korean soldiers were killed. The second conflict in August dragged on for months and southern forces were completely routed. Two ROK divisions were annihilated and hundreds of South Korean soldiers died in battle. Ultimately, DPRK forces regained complete control of the mountain. Despite the tensions that prevailed on the Korean peninsula and the fierce nature of these battles, however, they did not immediately produce the all out conflict that would begin just months later. The key reason was that while Korean leaders on both sides agitated for war, neither the United States nor the Soviet Union wanted such a conflict to break out. The United States demanded that its Korean client state show restraint or risk losing the military and economic assistance that it was receiving, and the Soviet Union refused to grant permission for a full-scale attack, without which the DPRK could not proceed.

Soviet policy changed in January 1950, when Stalin reversed his earlier position on a North Korean invasion of the South and gave Kim Il Sung permission to reunify the peninsula by force. Stalin believed that changing international now made it possible for such an invasion to succeed. Chinese communists were no longer fighting their civil war and could therefore send troops to Korea, if necessary. Most importantly, information from the United States indicated that the US would not intervene. Stalin first required Kim Il Sung to acquire the support of Mao Zedong, the leader of the People’s Republic of China, for his plans. After receiving assurances of support from the newly inaugurated People’s Republic of China, Kim began planning for the invasion in earnest. Soviet military advisers helped the Korean People’s Army (KPA) to plan the invasion and Moscow sent the necessary supplies. The initial plan called for an attack on the Ongjin peninsula. Sure that Seoul would counterattack, the DPRK would be able to claim that it had been attacked first. Three days before the scheduled date of attack, however, Kim Il Sung received reports that the South Koreans had learned of the DPRK’s plans, necessitating a change in strategy. Stalin agreed with Kim’s recommendation to change the plan and launch a broader invasion led by armored infantry across the 38th parallel. When this invasion finally occurred on June 25, it naturally alarmed Western leaders and led to a swift decision to mobilize for war. Thus, even though leaders from both Korean states aspired to reunify the peninsula by military means, Kim Il Sung and his Soviet and Chinese patrons bear primary responsibility for turning the border skirmishes into the larger and much more destructive military conflict that ensued.

The Course of the Korean War

The Korean War was not the brief campaign anticipated by the Soviets and promised by the North Koreans. Instead, it lasted for three years, involved troops from 17 other countries, and cost as many as 3.5 million lives. The Truman administration viewed the invasion as an act of Soviet aggression that must be stopped lest, like Nazi piecemeal aggression of the 1930’s, it lead to another world war. Truman turned to the U.N. to authorize the intervention to defend South Korea, partly in order to strengthen the newly created organization and partly in order to ensure domestic support. By going to the U.N. and having the organization recommend “police action” in Korea, the Truman administration could fight an “undeclared war” in Korea. The United Nations Committee on Korea decided swiftly that the DPRK had been at fault for the outbreak of the conflict, the U.N. swiftly ratified American plans, and fifteen countries committed their forces to fight under the UN flag.

In the first weeks of the war, DPRK forces proved far more formidable than the ROK army. By the beginning of August, American and South Korean forces had been driven back to the “Pusan perimeter,” a small area in southeastern Korea that encompassed the cities of Pusan and Taegu. Between early August and mid-September, 1950 DPRK forces controlled most of the Korean peninsula. During that time DPRK forces attempted to change political and social conditions in the southern half of the Korean peninsula. They sought to resurrect the people’s committees that had been dissolved by the American military government and to carry out land reform. Such reforms were not always welcomed by civilians, however, and in some cases DPRK forces had to resort to coercion and violence to accomplish them. Ultimately, however, DPRK forces controlled the southern portion of the peninsula for only a short period of time, as a dramatic reversal in the combat situation occurred in September.

On September 15, General Douglas MacArthur succeeded in making a daring amphibious landing at the port of Inch’ŏn. The harbor at Inch’ŏn was known for its dangerous tides that at their worst could destroy entire flotillas of ships. But MacArthur managed to land a fleet of 261 ships and 80,000 marines at this port while hardly sustaining any losses of either troops or ships. The DPRK lines were thus cut in two and quickly disintegrated. Within two weeks of the Inch’ŏn landing all of South Korea had been liberated from DPRK control. But neither the United States nor South Korea was content with repulsing the North Korean invasion. The Truman administration decided that Communism should not only be contained on the Korean peninsula but also rolled back. On September 30, 1950 American and South Korean forces crossed the thirty-eight parallel, in an effort to destroy the North Korean regime. DPRK forces continued to retreat quickly and within another month, nearly the entire Korean peninsula was under ROK control. Much as DPRK forces had sought to implement political and economic changes in South Korea when it fallen under their control, the United States and the ROK now sought to impose reforms on North Korea. The ROK sent Korean National Police units to take control of northern cities, where they hunted down communists and initiated political indoctrination campaigns. But like the DPRK occupation of the south, the ROK occupation of the north proved to be extremely short lived. In November 1950 another dramatic shift in the course of the war occurred when Chinese troops entered the war on behalf of North Korea.

China’s entry into the Korean War came as a shock to Americans, who had believed that the Chinese would not dare to fight the United States and that Beijing would not view the American advance as a security threat. The motives of Chinese Communist Party Chairman Mao Tse Tung for entering the conflict appear to have been ideological rather than strategic. Mao believed that China had an obligation to come to the aid of the DPRK because Korean troops had fought alongside Chinese Communist forces in China’s civil war and in the war of resistance against Japan. He also believed that entering the war in Korea would revive the flagging momentum of the Chinese revolution. Unprepared for the sudden Chinese onslaught, American and South Korean forces were forced to retreat rapidly. Within two weeks Chinese and DPRK forces had driven their adversaries out of North Korea and then began to move into the territory south of the parallel. On January 4, 1951 Seoul fell under Communist control once again. These were days of panic for American foreign policy makers in Washington. American officials and commanders considered the use of nuclear, chemical and biological weapons against Chinese forces during the early months of January 1951. General MacArthur continuously asked the Truman administration to grant him a commander’s discretion to use atomic weapons and criticized Truman when he did not agree to the request. Ultimately, however, the Truman administration decided not to use weapons of mass destruction, as they doubted their effectiveness when armies fought in such close proximity of each other.

U.N. forces eventually managed to recapture lost territory through several major combat operations carried out between January and March 1951. In April 1951 a major Chinese counterattack failed and ROK and UN forces under the new commander, General Matthew Ridgeway, forced their way back to the thirty-eighth parallel. While armistice negotiations began over the summer, both sides fortified their positions to the extent that neither was able to mount a further offensive. The war thus became a stalemate, continuing for two long years, as negotiations dragged on and casualties mounted.

The End of the Korean War

The negotiations for an armistice that opened in Kaesŏng in July 1951 proved tortuous. The United States was more inclined to negotiate than the Communists were, as the war was becoming increasingly unpopular at home and causing divisions between the United States and some of its allies. Believing that the continuation of the war was in the Soviet Union’s advantage as it tied US forces down in Asia and weakened America’s relationships with its European allies, Stalin encouraged Mao and Kim to take a hard-line in the negotiations. By 1952, both the Chinese and North Koreans were tiring of the severe losses they were suffering from the war, but, for different reasons, they continued fighting. Because Soviet prisoners of war (POW’s) forcefully repatriated from Europe at the end of World War II had been immediately sent to prison or shot as traitors, the US was determined to avoid repeating that mistake in Korea. It therefore insisted that POWs should be given the opportunity to state whether they wished to return to communist China or Korea, and if not, be repatriated to Taiwan or South Korea, instead. Such an arrangement was politically unacceptable to China.

After Eisenhower’s election, the Communist side became increasingly willing to negotiate. Mao feared that Eisenhower would escalate the conflict, perhaps into an all out war against the PRC. Eisenhower himself had promised that he would resolve the stalemate in Korea with “deeds” rather than “words.” Beijing feared that the U.N. would initiate new attacks on Korea’s east and west coasts and perhaps attack the Chinese mainland. Moreover, Eisenhower announced several weeks after his inauguration that the United States would not restrain Chinese Nationalist forces in Taiwan as the Truman administration had done. Mao seemed to have been genuinely concerned about these shifts in American strategy. The tough new stances adopted by the Eisenhower administration seemed to make the Chinese more willing to resume armistice negotiations in early 1953, although Stalin was still pressuring Mao to take a hard line. In March 1953, however, Stalin’s death would change the Communist strategy in the Korean War dramatically.

After Stalin’s death the Communist camp demonstrated a new willingness to negotiate. On February 22, 1953 General Mark Clark, who had assumed command of U.N. forces in Korea had sent a letter to Kim Il Sung and Chinese commander Peng Dehuai that included a new proposal on the issue of POWs. The Communist camp had not immediately responded but two weeks after Stalin’s death the new leadership in Moscow, worried about holding onto power at home and in Eastern Europe, took steps to end the war in Korea. The Soviet Council of Ministers passed a resolution in favor of a positive response to Clark’s letter. The council also sent letters to both Mao Zedong and Kim Il-Sung encouraging them to respond. The Soviets now began calling for the PRC to look for ways to bring an end to the conflict. On April 26 Armistice talks were resumed and the two sides continued to negotiate the contentious POW issue. On June 4 a major breakthrough was reached when the Communists accepted a U.N. proposal on the POW issue. The two sides agreed that POW’s would be released within 120 days of an armistice agreement and that a Neutral Nations Reparations Commission would interview individual POW’s to see which side they wanted to be released to.

Momentum towards the final conclusion of an armistice agreement had begun to build by June, 1953. But not all parties involved favored a swift end to the conflict. Syngman Rhee, the President of South Korea, now became a major thorn in the side of U.N. negotiators. Rhee did not want the war to end without the reunification of the Korean peninsula and his provocative behavior during the final months of the war nearly derailed the armistice talks. On June 18, Rhee released twenty-five thousand Korean POWs who said that they did not want to be repatriated to North Korea. This was in violation of the terms that had been agreed to during armistice negotiations and infuriated the Communist camp. Fortunately, Chinese propaganda placed the blame for the incident where it belonged – on the shoulders of Syngman Rhee and did not criticize the U.N. for this action. But Rhee continued to create problems. Although he agreed not to obstruct the armistice he sometimes dropped hints that the ROK might use force if reunification was not achieved in a political conference between North and South Korea to be held after the signing of the armistice. The Eisenhower Administration, however, pledged that it would not support any military offenses ordered by the Rhee government after the armistice had been concluded. America’s promise not to support Rhee if he unilaterally renewed hostilities eliminated one of the last major hurdles to the conclusion of an agreement. Exhausted by the duration and intensity of the war effort both sides finally signed an armistice agreement on July 27, 1953.

The conclusion of the armistice agreement stopped the brutal military conflict that had prevailed for three years. But it by no means meant an end to the feelings of enmity that existed between the two sides. The end of the war occurred primarily because a continuation of military combat was no longer in the interests of any of the nations involved. The U.S. and China would remain rivals for the next two decades. The issues that created such bitter enmity between North and South Korea during the war have continued to plague the Korean peninsula for the last six decades.

Works Cited

Bruce Cumings, The Origins of the Korean War Volume I'' and Volume II (Princeton, 1984 and 1991).

Bruce Cumings, ''Korea’s Place in the Sun'' (Norton, 1997).

Charles Armstrong, ''The North Korean Revolution, 1945-1950'' (Ithaca, 2002).

Chen Jian, ''China’s Road to the Korean War: The Making of the Sino-American Confrontation'' (Columbia University Press, 1994).

William Stueck, ''The Korean War: An International History'' (Princeton, 1995).

Kathryn Weathersby, “To Attack or Not to Attack? Stalin, Kim Il Sung and the Prelude to War,” Cold War International History Project Bulletin No. 5 (Spring 1995).

Kathryn Weathersby, “‘Should We Fear This?’ Stalin and the Danger of War with America,” Cold War International History Project Working Paper No. 39, (July 2002).

Gregg Brazinsky, ''Nation Building in South Korea: Koreans, Americans, and the Making of a Democracy
(University of North Carolina Press, 2009).