Sandwiched between Japan to the east, Russia to the northeast, and China to the northwest, the 600-mile-long Korean peninsula lay at the heart of Asian imperial rivalries throughout the twentieth century, just as it had for thousands of years before. For most of the first half of the twentieth century, Korea was annexed and exploited by Japan, the burgeoning imperial power of the East. The Japanese suppressed local rebellions with extreme brutality and simultaneously established some modern infrastructure on the peninsula in order to take advantage of the rich mineral deposits in North Korea. Japan's defeat in World War II finally brought Korea independence... of a sort.
Little actual fighting occurred in Korea during the Second World War, as the critical battles pitting the United States against the Japanese Empire occurred farther to the south. In July 1945, the leaders of the victorious Allied nations—the United States, Great Britain, and the Soviet Union—met at Potsdam, Germany, to make plans for the establishment of a new postwar world order. The fate of Korea was something of an afterthought, as most of the conference focused on contentious issues regarding what to do with Eastern Europe. But the Allies did agree that Japan should be forced to relinquish control over Korea, and that the country should be jointly occupied by the US and USSR, with the 38th parallel serving as a temporary boundary between the Soviet and American zones of occupation. As late as 9 August 1945—three days after the atomic bombing of Hiroshima and just six days before Japan's surrender—there were no Allied forces in Korea. On that date, the Soviets began their invasion from the north, meeting virtually no resistance as the Red Army moved southward through Korea. The Americans did not begin to organize their own occupation until a month later; the Soviets easily could have occupied the entire peninsula. But the Red Army halted its advance at the 38th parallel, carefully honoring the spirit and letter of the agreement reached at Potsdam by waiting patiently for their American friends to occupy the southern half of the country.
But the temporary wartime friendship between the Soviet Union and the United States was already beginning to fall apart. Korea soon became a pawn in a much larger game, as acrimony between the victorious superpowers transformed World War II Allies into Cold War enemies. By May 1946, international negotiations designed to reach an agreement on Korea's unified future broke down amidst the heightening tensions of the Cold War. The Soviets wanted to ensure that the country would be ruled by a friendly Communist government; the United States insisted, just as forcefully, that Korea not fall under total Soviet control. Both refused to relinquish control over their zones of occupation; what had been intended as a temporary division at the 38th parallel began to look more permanent.
In the North, with Soviet assistance, Kim Il Sung began organizing an authoritarian Communist regime. Meanwhile, in the South, Korean exile Syngman Rhee—who had spent much of his life living in the United States—established his own administration, no less authoritarian than Kim's but ferociously anticommunist and backed by the Americans. The newly established United Nations attempted to resolve the matter in late 1947, when it created a temporary commission to supervise elections in order to reunify Korea as one independent country. But the Communists boycotted the elections, allowing the unpopular Rhee to win, with a dubious mandate, in the South, while no elections at all were held in the North. By the fall of 1948, South Korea under Rhee had declared itself the independent Republic of Korea. North Korea then proclaimed itself the People's Democratic Republic under Kim's rule. The South received recognition from the western powers and the UN, while the eastern bloc recognized the North. The governments of both Kim and Rhee claimed to represent the entire country, and both were eager to reunify Korea under their own leadership—by force, if necessary.
Between 1946 and 1950, Koreans endured a vicious undeclared civil war in which Communist and anticommunist insurgents slaughtered each other with increasing brutality. Historians now estimate that more than 100,000 Koreans died during this period—all killed by other Koreans, all before what Americans usually consider to be the beginning of the Korean War proper in June 1950. During this phase of guerilla fighting, Kim's Communists seemed to have the upper hand, but only just slightly. Many Koreans, even non-Communists, objected to Rhee's apparent willingness to accept partition of the country and his over-reliance on American aid to support his regime; Kim, by contrast, seemed to have stronger nationalist credentials and insisted absolutely upon the need to reunify the country. Several of South Korea's best army units defected, en masse, to the Communists. Still, Kim's seeming advantage in the civil war wasn't enough to topple Rhee's government, and the prolonged guerilla violence made it impossible for Korea to begin rebuilding its economy and infrastructure, long neglected by Japanese occupation. By 1950, Korea was, in the words of historian Walter LaFeber, little more than "a Cold War-wracked country which lacked nearly everything except authoritarian rulers, illiteracy, cholera epidemics, and poverty."15
Kim Il Sung was a brutal Communist dictator. In the aftermath of the Korean War, he built in North Korea one of the most repressive totalitarian regimes ever seen on earth; North Koreans continue to suffer the consequences even today. At the same time, Syngman Rhee was no champion of freedom and democracy. Rhee muzzled the press through systematic censorship and ordered that tens of thousands of his domestic opponents be thrown into jail as political prisoners. Forces loyal to Rhee murdered thousands of leftists and others he feared might be disloyal to his regime. Even after North Korea launched its invasion in June 1950, Rhee seemed to devote as much attention to wiping out dissidents as he did to defending his country; throughout the so-called "summer of terror" that followed the invasion, South Korean military and police executed an estimated 100,000 people deemed unfriendly to Rhee's regime.
Thus neither side in the Korean conflict was exactly a paragon of traditional ideals of freedom and self-determination. The inherent goodness of Syngman Rhee would certainly provide no justification for intervention in the Korean War. As historian James L. Stokesbury has argued, "a perfectly objective observer might well have concluded that one side was not worth supporting at all, and the other was only marginally better."16
As miserable as political and social conditions in Korea—both North and South—may have been, the country's strategic significance seemed to be growing. Korea still sat, as it always had, in its vital location between the Soviet Union, Japan (now an emerging American ally), and China (which "fell" to the Communists after a long civil war in 1949). Both the United States and Soviet Russia viewed the Korean peninsula as a strategically valuable position, and both hoped that their respective Korean allies could achieve reunification of the country on their own terms. But neither wanted to risk a nuclear World War III over Korea, either.
Thus both superpowers' policies toward Korea from 1945 through 1950 followed a cautious, almost delicate path. How hard could either side push in Korea without provoking its enemy into a broader war that neither wanted? Was Korea worth fighting for? More importantly, did the other side think Korea was worth fighting for?
In January 1950, American Secretary of State Dean Acheson gave an important speech to the National Press Club in Washington, D.C. He vowed that the United States would always be the best ally for those in Asia who sought "their own national independence," arguing that anyone who sought aid from the USSR would end up dominated by the totalitarian Soviets. During the same speech, however, Acheson made a fateful announcement. The United States had a vital "defensive perimeter," he said, a line that the Soviets could never cross without threatening America's core national security interests. In the Pacific, Acheson said, that line ran from the Aleutian Islands off Alaska to Japan, through the Ryukyu Islands between Japan and Taiwan, and south to the Philippines. Conspicuously left outside the American "defensive perimeter": Korea.
It's not clear that Acheson meant to send a signal to Moscow that the United States wouldn't fight to preserve Rhee's government in South Korea, but that's exactly what Soviet dictator Josef Stalin interpreted Acheson's remarks to mean. Kim had been begging Stalin to authorize and support a full-fledged Communist invasion of South Korea for some time; Stalin, fearful of possible American reprisals, had consistently held his Korean ally in check. But in the wake of Acheson's "defensive perimeter" speech, he finally gave Kim the green light to try to topple Rhee's regime by armed invasion.
On 25 June 1950, tens of thousands of well-trained and well-armed North Korean troops suddenly poured across the 38th parallel, quickly forcing Rhee's overwhelmed army into a desperate retreat.
While Communist tanks rolled through the South Korean countryside, US President Harry Truman cut short a visit with his family in Independence, Missouri, returning immediately to Washington for emergency meetings with his top military and political officials. In the more intellectually detached analysis of six months earlier, Korea may have seemed outside the vital security perimeter of the United States. But now, with Communist forces rampaging through the country, the fall of Korea suddenly felt like a much more dire blow. Assuming that Stalin rather than Kim had been the driving force behind the invasion, and fearing—incorrectly, as it turned out—that the invasion was only the first phase of a broader Soviet expansionist aggression all around the world, Truman almost immediately resolved to intervene in the conflict. In Truman's mind, Communist aggression simply could not be allowed to go unchecked. At a crisis meeting of Truman's military council held on 25 June, General Omar Bradley, the nation's highest-ranking military officer, captured the general sentiment when he said, "we must draw the line [against Communist expansion] somewhere.... The Korean situation offered as good an occasion for action in drawing the line as anywhere else."17
Thus South Korea—an impoverished and underdeveloped nation ruled by an unpopular autocrat—suddenly became a cause worth fighting for, the first hot spot of the emerging Cold War.
On 27 June 1950, just three days after Kim launched his invasion, Truman sent his diplomats to the United Nations to seek international endorsement of the decision he had already made to commit American forces to the Korean conflict.
The UN had been created only five years earlier. The organization was originally proposed by President Franklin D. Roosevelt to serve as a kind of joint governing council through which the victorious Allied powers of World War II—the United States, Soviet Union, Great Britain, France, and China—could peacefully and cooperatively resolve international disputes. But by 1950, this cooperative vision of the United Nations' potential had already largely collapsed under the pressures of the burgeoning Cold War.
In 1949, the long-running Chinese Civil War ended when the forces of Communist leader Mao Zedong drove the Nationalist (and pro-American) government of Generalissimo Chiang Kai-Shek into a retreat to the island province of Taiwan. As in Korea, both Chinese governments—Mao's Communists and Chiang's Nationalists—claimed to be the rightful rulers of the entire country, encompassing both Taiwan and the mainland. The dispute spilled into the United Nations because Chiang's Nationalists had controlled China's powerful permanent seat on the UN Security Council since 1945. But in the wake of Mao's victory, the Soviets and their allies argued that the Communist People's Republic of China (which now controlled the entire country save Taiwan) rather than Chiang's Nationalist Republic of China (which now controlled only Taiwan) ought to fill China's seat on the Security Council. When the Western democracies, led by the United States, refused to turn over China's UN representation to Mao's Communists, the Soviets walked out of the international organization in protest.
Somewhat stupidly, the Soviets refused to end their UN boycott even after Kim's invasion threw the world into sudden crisis in June 1950. Therefore, when the Americans went before the Security Council to ask for a resolution branding the North Koreans as aggressors and committing the international community to defending South Korea's sovereignty, no Soviet representative was present to cast a veto. Thus, officially, the American intervention in the Korean War was undertaken not in the interest of the United States but instead at the request of the United Nations; the Korean War, technically speaking, was not a war at all but actually a United Nations "police action." US General Douglas MacArthur, who led the American intervention in Korea, was theoretically the supreme commander of "UN forces." In reality, though, the UN resolutions provided little more than an international fig leaf to cover a unilateral American decision to fight in Korea. Out of the more than 5.7 million soldiers who comprised the "UN forces" in Korea, only about 40,000—less than one percent—came from countries other than the United States. MacArthur himself later admitted that he "had no direct connection with the United Nations whatsoever," that his orders came from American rather than UN leaders.18 Most importantly, the crucial decision to throw American ground troops into the Korean conflict was made by President Truman on 27 June 1950—several hours before the UN Security Council passed its resolution (by a vote of 7 to 1, with Yugoslavia opposing and India, Egypt, and the Soviet Union abstaining) authorizing international intervention in Korea.
That the United Nations allowed itself to be drawn into the Korean War as something of a pawn of the United States proved that Franklin Roosevelt's original idea that the organization could serve as the cornerstone of a cooperative world order was well and truly dead. In the Cold War, superpower conflict rather than international cooperation would be the most powerful force shaping global diplomacy. The UN's participation in the Korean War was less a sign of its strength than its weakness.