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The US, the USSR, and the the Korean War

By Kathryn Weathersby

When the Soviet-supplied tanks of the North Korean army crossed the 38th parallel, the US and its allies reacted with intense alarm.

Table of Contents

Attack on South Korea

From the perspective of today, more than a decade after the forty-year Cold War ended with such apparent ease, it can be difficult to understand the fears that drove the leaders of the Soviet Union, the United States, and their respective allies to create a highly militarized global stand-off in the years following World War II. Even harder to understand is why the Cold War took its lasting shape in response to the North Korean invasion of South Korea on 25 June 1950. The Korean peninsula, liberated from 35 years of Japanese rule by the defeat of Japan in 1945, was not a central concern of either the Soviets or the Americans. It had hardly figured into the discussions of the postwar territorial settlements. Partly for that reason its joint Soviet/American occupation had ended with an unanticipated and messy division into two hostile states, as post-colonial Korean politics polarized along the axis of the two occupying powers. By 1950 the tension between the Soviet-backed Democratic People’s Republic of Korea (DPRK) in the North and the American-backed Republic of Korea (ROK) in the South was regarded as one of the world’s trouble spots, but neither side in the emerging East/West struggle placed Korea very high on its list of priorities.

Nonetheless, when the Soviet-supplied tanks of the North Korean army crossed the 38th parallel—the artificial boundary between the two states—in the early morning hours of Sunday 25 June 1950, the administration of US President Harry S. Truman, as well as the governments of all allied Western powers, reacted with intense alarm. The statesmen in power in 1950 had all experienced the immense trauma of the Second World War, which had ended only five years earlier. Their chief aim was therefore to prevent another such catastrophe. The surprise tank-led invasion of South Korea, which they took to be a Soviet action by proxy, immediately evoked in their minds the piecemeal aggression by Germany, Italy and Japan in the 1930’s that, because it had not been resisted, had culminated in World War II. As President Truman later wrote, “In my generation, this was not the first occasion when the strong had attacked the weak. I recalled some earlier instances: Manchuria, Ethiopia, Austria…Communism was acting in Korea just as Hitler, Mussolini, and the Japanese had acted ten, fifteen, and twenty years earlier.” President Truman concluded that if the North Korean attack went unchallenged, “it would mean a third world war, just as similar incidents had brought on the second world war.”

The President’s perception of the danger the North Korean attack signified was shared by of his foreign policy advisers, as well as their counterparts throughout the Western world, who viewed the attack as indicating a dangerous new willingness on the part of Soviet leader Joseph Stalin to expand the territory under Soviet control beyond the boundaries that had been tacitly accepted at the end of the war. Fearing that the Soviet Union would move next into Western Germany, Iran, or some other soft spot along the lengthy Soviet border, the President and his advisers unanimously agreed to send US military forces to defend South Korea.

Because the Truman administration also believed that world peace could only be preserved if the newly established United Nations became an effective defense against aggression, they brought the Korean issue to the UN Security Council. With the Soviet Union continuing its boycott of the UN to protest that body’s exclusion of the People’s Republic of China, the Security Council passed a resolution calling on North Korean forces to withdraw and all UN member states to “furnish such assistance to the Republic of Korea as may be necessary to repel the armed attack and to restore international peace and security in the area.” The intervention on behalf of South Korea was thus officially a UN, rather than US, action. Americans staffed the UN Command and provided the overwhelming majority of foreign troops, but fourteen other countries eventually committed military forces as well: the United Kingdom, Australia, Canada, New Zealand, France, Turkey, Greece, the Republic of China, the Philippines, Thailand, South Africa, Ethiopia, and Columbia.

American fears of communist expansion were especially acute in 1950 because the previous fall the Chinese Communist Party had finally succeeded in coming to power in mainland China, forcing the Nationalist troops to retreat to the island of Taiwan. With the huge country of China now added to the Soviet bloc, it was feared that the industrial powerhouse of Japan might succumb next, or the resource-rich countries of Southeast Asia. If the Soviet-based alliance gained access to a majority of the world’s key resources, it might prove impossible to defeat them should they attack the United States.

Since China bordered Korea and had longstanding interests there, the Truman administration assumed that the Soviets had planned the attack on South Korea in conjunction with the new communist government in Beijing. In order to prevent the Chinese Communists from following the action in Korea with an attack on Taiwan, the President dispatched the US 7th Fleet to the Taiwan Straits, beginning the US defense of the island that remains the single greatest obstacle American relations with Beijing. He also committed the United States to support the French in Indochina, who were fighting against communist insurgents, setting the stage for the American war in Vietnam the following decade. To shore up Japan against a possible communist attack, the administration began to prepare for a separate peace treaty with Tokyo that would exclude the Soviet Union, whose forces had joined those of the US at the end of the war against Japan. To this day, Moscow and Tokyo have still not concluded a peace treaty, and their relations remain strained.

In Europe, the war in Korea led the Western powers to transform the recently established North Atlantic Treaty Organization (NATO) from a loose association into a real military alliance. The perceived need to defend against a possible Soviet attack on Western Europe was so great that NATO members even agreed to the rearmament of West Germany, their recently defeated enemy. In the United States, the attack on South Korea persuaded policy-makers that the extensive demobilization of American armed forces after the conclusion of World War II had left the country unable to meet the new threat of Communist aggression. Congress therefore tripled US defense spending, setting in motion the arms race that would continue for the remainder of the Cold War.

Russian and Chinese Evidence

The partial opening of Russian archives after the collapse of communist rule in 1991, and the more limited release of Chinese archival documents have made it possible for historians to test whether the perceptions in the non-communist world that led to such far-reaching and long-lasting consequences were, in fact, accurate. Was the decision to attack South Korea made in Moscow? If so, what did this signify about Soviet intentions? What was the Chinese role and what were Beijing’s aims?

The first question has been the easiest to resolve. Russian archival records show that North Korean leader Kim Il Sung raised the issue of using military means—rather than subversion, which had been tried and failed—to reunify his country under Communist rule. However, since the DPRK was economically, politically and militarily dependent on the Soviet Union, the decision to undertake such a difficult and risky task could only have been made by the Soviet leadership. Russian records reveal that Kim Il Sung first asked Stalin for permission to invade the South in March 1949, and the Soviet leader turned him down since American troops were still in the ROK. Kim was allowed only to counterattack in case of an invasion from the South, which was a real possibility since southern leaders similarly wished to reunify the country under their control. In August 1949 Kim raised the question, after US troops had withdrawn from the ROK. He was again refused, on the grounds that the Korean People’s Army (KPA) was not sufficiently strong to guarantee a quick victory and if the war were prolonged, the Americans would have time to send their troops to aid the ROK. In January 1950 Kim once again pleaded for an audience with Stalin to discuss the possibility, particularly in light of the victory of the Chinese Communist Party the previous October. This time Stalin informed his North Korean protégé that he would “help him in this matter,” but that it “must be organized so that there would not be too great a risk.”

While Kim Il Sung and his foreign minister, Pak Hon Young, were in Moscow the month of April to plan the campaign, Stalin explained to them that he was finally able to support their request because the international situation had changed. First, the victory of the Chinese Communist Party had freed Chinese troops for service in Korea, should the DPRK need help. The establishment of the People’s Republic of China moreover showed the weakness of the West. Americans had not fought to prevent a Communist victory in China; they thus would not fight for the smaller prize of Korea. Second, the Sino/Soviet alliance concluded in February made the US even more hesitant to challenge the Communists in Asia, as did the Soviet’s acquisition of the atomic bomb the previous summer. Stalin noted that intelligence from the US showed that “it really is so. The prevailing mood is not to interfere.”

The Soviet leader nonetheless remained worried that the US might intervene. He therefore emphasized to Kim and Pak that the war must be won quickly before the Americans had time to land troops. He also made it clear that he would under no circumstances send Soviet troops to Korea. The USSR would provide the necessary advisors, weapons, and supplies, but Kim would have to rely on China if he needed troops reinforcements. In principle, Stalin did not in principle oppose fighting against the United States, but with the USSR devastated by World War II, the Soviet leader desperately wanted to avoid war with America until the Soviet Union was prepared to win it.

Were Western political leaders therefore correct to view the North Korean attack as constituting a new level of aggression that if not resisted would have emboldened the Soviets to invade other countries? This question remains open to differing interpretations. Russian archival records reveal that Stalin’s aim in Korea was to ensure that the peninsula be brought under the control of a “friendly” government in order to prevent Japan from again using Korea as a staging ground for an invasion of the Soviet Far East. Stalin’s motives for the attack on South Korea were therefore defensive, though his strategy of gaining security through annexing territory was in effect aggressive. The invasion was not planned as part of a wider assault, nor was it a test of American resolve; Stalin took the action in Korea only because he believed the United States would not intervene. However, I would argue that even though he did not intend the invasion to be a test of resolve, it in fact became one. Just as Stalin had concluded from American non-intervention in China that the Soviet Union had an opportunity to advance in Korea, he would likely have drawn the same conclusion about opportunities elsewhere if the US had not resisted the attack on South Korea.

As for China’s role in the decision, Russian documents reveal that since Stalin counted on being able to use Chinese troops as reinforcements, he stipulated that the operation could only go forward if Kim Il Sung secured the approval of Chinese leader Mao Zedong. The North Korean leader accordingly went to Beijing in May, where Mao, after confirming Kim’s message with Stalin via telegram, approved the plan. Strictly speaking, therefore, the decision to invade was made by Mao as well as Stalin. However, in actuality Mao had no choice but to agree, given his dependence on his recently concluded alliance with Moscow, even though, as Chinese sources reveal, he would have preferred that the Korean action be delayed until after he had conquered Taiwan. The essential decision was therefore Stalin’s. Moreover, the Chinese were neither consulted nor even kept informed about the plans for the attack after Kim left Beijing. The evidence therefore suggests that the conflation of Chinese and Soviet responsibility for the invasion was misplaced. One could argue that dispatching the US 7th fleet to the Taiwan Straits was not justified, since the attack on South Korea did not signify that the Chinese Communists were preparing to expand their rule beyond China’s borders. This misperception proved costly, as the eventual entry of Chinese troops prevented a UN victory and transformed the war into a prolonged, bloody, and indecisive conflict.

Events on the Ground

With inferior weapons and training, the ROK army was unable to stop the Soviet tanks of the Korean People’s Army (KPA). Nor were the first detachments of American troops able to stop the North Korean advance, having been hastily brought over from occupation duty in Japan, where they had been inadequately trained and supplied. By late summer US and South Korean forces were confined to a small area around the southern port of Pusan, and it appeared that the North might well be victorious. However, the KPA’s supply line was now dangerously extended, and as the Chinese leadership warned Kim Il Sung, the Americans could cut his line in two by landing troops behind the front line. That was, indeed, what US General Douglas McArthur succeeded in doing on September 15, braving the treacherous tides at the port of Inchon, just west of Seoul. UN forces then quickly retook Seoul and severed the KPA line.

The North Korean army rapidly disintegrated and on September 30 UN forces crossed the 38th parallel into DPRK territory. Faced with imminent defeat, Kim Il Sung first asked Stalin to send troops, then when the Soviet leader still refused to risk a direct conflict with the Americans, the North Korean leader reluctantly turned to Mao Zedong. Since the Chinese had for centuries dominated Korea’s affairs, Kim Il Sung feared that the presence of their army might undermine his hold on power. Many in the Chinese leadership, on the other hand, were reluctant to intervene in Korea because they had just ended their lengthy struggle for power and desperately needed to turn their attention to domestic reconstruction. While the Chinese leadership deliberated, UN forces advanced rapidly, taking Pyongyang and moving northward almost to the Chinese border. When Stalin received a telegram on October from Beijing informing him that the Chinese would not, after all, be able to send troops to Korea, he sent an order to Kim Il Sung to evacuate his forces from Korean territory. Even at the cost of US victory in Korea, the Soviet leader was not willing to send his troops into battle against the Americans.

The next day Stalin received another telegram from Beijing informing him that the Chinese had decided to intervene after all; Mao Zedong had persuaded his comrades that American “arrogance” must be answered, and that war with the US would renew the revolutionary spirit of the Chinese people as well as protect the border with Korea. The Soviet leader promptly cancelled the evacuation order and waited to learn the results of the fight between his junior ally and his chief foe. Using their long experience with guerilla warfare, the Chinese generals allowed the UN forces to penetrate deeply into the frozen and rugged mountains of North Korea. Under cover of night, the scantily clad and armed Chinese troops crossed the border in large numbers and surrounded the unsuspecting UN forces. Once the seasoned Chinese troops attacked, UN forces were thrown into disarray. Stalin watched in amazement as the technologically superior Americans retreated before the ill-armed Chinese. Over the harsh winter, UN forces were driven out of North Korea and the Communist armies recaptured Seoul. In the spring, however, a new commander, General Matthew Ridgeway, rallied UN forces and pushed the front line back approximately to the 38th parallel. Their last campaign having failed to achieve victory, the Chinese secured Soviet approval to open armistice negotiations. Their intention was to buy time in order to reinforce their positions, preparing for a new offensive in the fall. By August, however, both sides were dug into the mountainsides so successfully than neither side was able to advance. The war remained a stalemate for the next two years, while armistice negotiations dragged on at a snail’s pace.

The main issue that delayed the negotiations on an armistice was the question of repatriation of prisoners of war. The United States feared that the communist side would keep some UN prisoners to use as forced laborers, as they had done with Japanese and Germans following World War II. The UN side was also concerned that Chinese and Koreans who had been drafted into the Communist armies against their will would be forced to return to the PRC or the DPRK despite their desire to go to Taiwan or South Korea. Many in Western governments were determined not to repeat the terrible experience of Soviet POW’s at the end of World War II, who despite desperate pleas not to be forced to return to the USSR were shoved onto trucks and planes, only to be imprisoned or executed upon their arrival in the Soviet Union. Moreover, as the UN forces remained unable to break through the Chinese/North Korean defenses, winning the POW issue became a substitute for victory. Similarly, the Chinese and North Koreans could not tolerate the loss of face they would suffer if large numbers of prisoners chose to repatriate to the other side.

As the stalemate continued and the negotiations dragged on, the US turned increasingly to aerial bombardment to achieve some sense of victory. While Stalin did not send Soviet ground forces to Korea, since China did not yet have an Air Force, he sent Soviet Air Force units to guard the bridges over the Yalu River and the bases on the Chinese side of the river. Soviet pilots wore Chinese uniforms, however, their planes were marked with Chinese symbols, and they were forbidden to fly over enemy-held territory lest their presence be revealed should they be shot down and captured. It was nonetheless obvious to the UN side that these pilots were Russian, but the Truman administration joined forces with Moscow to keep their presence secret to avoid inflaming the American public, who might call for war with the Soviet Union. This two and a half year secret air war between Soviet and American pilots marked the largest and most sustained military conflict between the two superpowers over the entire course of the Cold War.

The ferocity of the US bombing of North Korea provided excellent ammunition for communist propaganda, which was exploited fully. The last year of the war, as the destruction of the physical infrastructure led to outbreaks of serious infectious diseases in North Korea, the Communist side began to accuse the US of intentionally spreading these diseases by dropping bacteriological weapons over Korea. Since the US was sheltering the leader of the Japanese unit that had developed and used BW against China during WWII, this charge had some credibility. Along with reports of the damage from the bombing, it served to rally the people of the Soviet bloc to oppose American actions and inspire serious anti-American protests in Western Europe. A small number of Russian documents on the BW allegations analyzed and published by the CWIHP in 1998 showed those claims to have been fabricated by the Soviets, Chinese, and North Koreans. The charges are still proclaimed in China and North Korea, however, where they are widely believed.

Once the war became a stalemate and therefore no longer threatened to bring American forces to the Soviet border, Stalin urged the Chinese and North Koreans to maintain a firm line in the negotiations, apparently seeing the war as bringing more advantages than disadvantages to the Soviet Union: it tied down American forces while providing an excellent opportunity to gather intelligence on US military capabilities; it drained American economic resources, and caused strains in relations within the Western alliance. The DPRK leadership, on the other hand, wished to bring the war to an end by early 1952, so that the destruction it was suffering from the bombing would cease. Evidence on the Chinese position is less definitive, but there are indications that by late 1952, Mao Zedong also had grown weary of the heavy casualties his troops were suffering. Stalin’s sudden death in March 1953 freed the Communist side to bring the war to an end. His successors in Moscow immediately took steps to reach a negotiated settlement. The Chinese continued to fight for a few more months, however, partly in the hope that the new administration of Dwight D. Eisenhower might offer them a better deal in Korea.

An armistice was finally signed on 27 July 1953, but a peace treaty has not been concluded. Both sides remain in a high state of vigilance along the heavily fortified border and US troops remain in Korea. Despite the collapse of the Soviet Union in 1991 and the end of Communist rule in Eastern Europe, the division of Korea remains as it was at the conclusion of the devastating war of 1950-53.

About the Author

Kathryn Weathersby is Senior Associate at the Woodrow Wilson Center's History and Public Policy Program and the Coordinator of the Center's North Korea Documentation Project. (Ph.D. Indiana University, 1990)