In order to do so, Kim built up a formidable army which was armed by the Soviets. His army was also bolstered by the arrival of veteran Korean fighters from China after the end of the Chinese civil war between the Communist and the Nationalists in which the Communists under Mao had triumphed. On the other hand, Rhee's government was relatively weak due to the communist insurgency in the south and his army had not been armed to the same level as that of North Korea by the United States.
Nevertheless, Stalin did not approve of such an attack at first because he did not want a direct confrontation with the United States at that stage. After the Soviet testing of the atomic bomb in 1949, and the success of the communist revolution in China in the same year, Stalin gained more confidence. Hence, when Kim Il Sung approached him in the spring of 1950 to seek his [Stalin's] approval for military action across the 39th parallel with the assurance that it would be a quick, decisive war, Stalin gave him his go-ahead (Weathersby, 95). In this way, the main cause of the Korean War can be attributed to the ongoing civil war between the left-wing groups seeking radical land-reforms and the right wing conservative elite of landowners, businessmen, and manufacturers who sought to retain the status quo.
The Korean War as Part of the Cold War Confrontation
Even if the primary reason for the start of the Korean War is assumed to be the internal conflict between the left and right wing groups within the country, it would never have escalated into a major international event in the absence of the Cold War conflict between the two world major powers at the time. Russia's experience of foreign aggression on its territory during the World Wars had convinced it to seek buffer states around its territories for security reasons, both in Europe and in Asia. Moreover, the U.S.S.R. As the flag-bearer of Communist ideology felt obliged to support spread of the communist revolution around the world in the post World War II world.
As the Soviet Union started to support Communist movements around the globe, the United States feared a "domino effect" and sought to counter the Soviet influence through a policy of aggressive "containment." This policy of 'containment' meant that the United States would seek to confront the spread of Communism wherever it felt that it intruded into its area of influence. Immediately after the end of World War II, the United States was concerned about the 'containment' of Soviet influence in Europe. It also sought to protect its interests in Japan but was somewhat ambiguous about the extent of its interest in protecting Korea. Such ambiguity was reflected in the U.S. Secretary of State Acheson's speech before the National Press Association in January 1950, in which he placed Korea outside of the American defense perimeter in Asia. This assertion by Acheson is in fact cited by some historians for being, at least partly responsible for the start of the Korean War as it may have been construed as an indication by North Korea and the Soviet Union about United State's lack of seriousness in directly defending South Korea against a Communist take-over (Weathersby, 92).
As it turned out, Stalin was wrong in his assessment that the United States would not react strongly to a military action by North Korea. As soon as the heavily armed North Korean forces crossed the 38th parallel on June 20, 1950 led by Soviet-made tanks, Washington and its allies were sure that the attack had been planned in Moscow and that it signified a new Soviet aggressiveness. They assumed that if the West did not resist, there would be similar attacks elsewhere along the Soviet Union's vast periphery, in Europe and perhaps the Near East. Within days of the attack, the United States and 15 other members of the United Nations had committed their armed forces to a defense of South Korea, thus escalating an internal conflict on the peninsula into a major international war (Weathersby, 92).
Moreover, in its Cold War-mindset the Truman administration thought of the Communist threat as a monolith. It assumed that Mao Zedong's new communist regime in Beijing had also helped plan the attack, and the action may be part of a 'master plan' by the Chinese Communists to also attack Taiwan -- where their Nationalist foe, Chiang Kai-shek had fled after being defeated in the Chinese civil war. The U.S. Seventh Fleet was quickly dispatched to the Taiwan Straits, not only committing the United States indefinitely to the defense of Taiwan but making enemies with Beijing, which the Chinese would repay only months later to rescue North Korea from certain defeat.
In some ways, therefore, Burton I. Kaufman, a leading historian of the Korean War is quite right in labeling the conflict "a great power struggle between the United States and the Soviet Union superimposed on a civil war between North and South Korea." (Kaufman, 5)
The United States' View
The official U.S. view about the causes which led to the Korean War is that it happened as a result of an international Communist conspiracy to expand its influence over the whole of the Korean peninsula, formulated with the connivance and active support of the North Koreans, the Soviet Union, and Communist China. Many people in the United States were also inclined to believe it was a diversion set up by the Soviets to draw attention from a war to be launched in Europe. The "diversion theory" has proven to be inaccurate, but the belief continues that the invasion somehow fit into the larger Communist desire to rule the world. The U.S. administration also purported to have been taken by surprise at the all-out attack by North Korean army on June 20, 1950 when it crossed the 38th parallel. Both these views -- that the attack by North Korea was a pre-planned Communist strategy and at the same time being taken by surprise, do seem a little contradictory. Add to this the fact that the Americans had all but withdrawn its troops from Korea by 1949 and had only lightly armed the South Korean army, which was no match for the much stronger North Koreans, and the whole U.S. policy towards Korea in the post World War II years seems perplexing. In order to understand the seemingly contradictory acts of the U.S. government in Korea we have to appreciate the fact that the U.S. wanted to cut down its military spending after the end of World War II. It is also a fact that President Truman, unlike his predecessor -- President Roosevelt, was no visionary strategist. He had to handle the Republicans who were anxious to take back the country into its customary isolationist mode and the Congress was not too keen to sanction increased budgets for the military. In such a situation, the Truman administration had to prioritize its international commitments. Its first priority lay in Europe and Asia took a back seat as far as the American commitment for defense against Communism was concerned; in Asia too, the U.S. defense perimeter consisted of Japan, the Philippines and the defense of Taiwan against possible attack by Communist China. As far as Korea was concerned, the U.S. had an agreement with the Soviet Union about division of the peninsula at the 38th parallel and it was convinced that the Soviets would not risk a direct confrontation with the United States on the peninsula. Hence, in the back drop of a depleted army budget, when General MacArthur, the Far Eastern commander and head of the occupation of Japan, endorsed withdrawal of U.S. troops from Korea in the spring of 1949, the State Department agreed to pullout its combat soldiers from Korea. By the end of June the withdrawal was complete save for a permanent deployment of a U.S. military advisory group. The U.S. continued to provide military and economic aid to South Korea but deliberately did not build up the South Korean army to a level where it would be encouraged to attack the North Koreans.
Hence, in some ways, the apparently perplexing U.S. contention that it was taken by surprise at the North Korean attack on its southern neighbor may not be altogether false. What is more surprising is the American administration's ambiguity regarding U.S.'s commitment to defend ROK in case of attack by the Communists. In particular, the Secretary of State Dean Acheson's infamous speech of January 12, 1950, implying that the United States could not guarantee South Korea's security in case it is attacked, was a real disaster.
The Soviet Role in the Korean War
Release of secret archival material after the collapse of the Soviet Union has revealed that Stalin was so determined to avoid a military confrontation with the United States, fearing that the…