While the end of World War II brought peace and prosperity to most Americans, it also created a heightened state of tension between the Soviet Union and the United States. Fearing that the Soviet Union intended to "export" communism to other nations, America centered its foreign policy on the "containment" of communism, both at home and abroad. Although formulation of the Truman Doctrine, Marshall Plan, and the Berlin Airlift suggested that the United States had a particular concern with the spread of communism in Europe, America's policy of containment extended to Asia as well. Indeed, Asia proved to be the site of the first major battle waged in the name of containment: the Korean War.
In 1950 the Korea Peninsula was divided between a Soviet-backed government in the north and an American-backed government in the south. The division of Korea into two halves had come at the end of World War II. In August of 1945 the Soviet Union invaded Korea, which had been under Japan's control since 1910. Fearing that the Soviets intended to seize the entire peninsula from their position in the north, the United States quickly moved its own troops into southern Korea. Japanese troops surrendered to the Russians in the north and to the Americans in the south. In an effort to avoid a long-term decision regarding Korea's future, the United States and the Soviet Union agreed to divide Korea temporarily along the 38th parallel, a latitudinal line that bisected the country. On that day, North Korean troops coordinated an attack at several strategic points along the parallel and headed south toward Seoul. The United Nations Security Council responded to the attack by adopting (by a 9-0 vote) a resolution that condemned the invasion as a "breach of the peace." The Council did not have a Soviet delegate, since 6 months prior, the Soviet Union had left to protest the United Nation's refusal to seat a delegate from China. President Harry S. Truman quickly committed American forces to a combined United Nations military effort and named Gen. Douglas MacArthur Commander of the U.N. forces. Fifteen other nations also sent troops under the U.N. command. Truman did not seek a formal declaration of war from Congress; officially, America's presence in Korea amounted to no more than a "police action."
So why did the United States become involved in the Korean conflict?
Events in Asia also contributed to an increased sense of insecurity. In 1949 China underwent a revolution that brought Mao Zedong and his Communist party into power. The nationalists, led by Chiang Kai-Shek, had retreated to the island of Formosa (Taiwan) while they continued their war with mainland China. Mao quickly moved to ally himself with the Soviet Union, and signed a treaty with the Soviets in 1950. The Truman administration faced criticism from Republicans who claimed he had "lost" China. They criticized him for not providing enough aid to the Chinese nationalists. The suggestion by Secretary of State Dean Acheson that the administration recognize the communist government of China only gave them more ammunition for their attacks.
Truman's statement of June 27 illustrates his concern with communist aggression and expansion. In it, Truman argues that "communism has passed beyond the use of subversion to conquer independent nations and will now use armed invasion and war." Truman's statement suggests that he believed the attack by North Korea had been part of a larger plan by communist China and, by extension, the Soviet Union. The President believed that the Korean situation was similar to that of Greece in 1947. He informed his advisors that he believed the invasion was "very obviously inspired by the Soviet Union." This gave America a moral imperative to act. "If we don't put up a fight now," Truman observed to his staff, there was "no telling what they'll do." His concern over the future of anticommunist governments in Asia showed in his public statement. Truman pledged to defend Formosa (Taiwan) from attack and to support French forces in Indochina, a conflict that would eventually escalate into the Vietnam War. Yet Truman had no wish to provoke a full-scale war with the Soviets. By blaming "communism" in the statement, as opposed to the Soviet Union, Dean Acheson later explained, the administration sought to give the Soviets a "graceful exit" and not provoke open confrontation with Russia.
Truman's statement also reflected a new military order. Although the United States took the lead in the Korean action, it did so under the rubric of the United Nations. Truman made it clear that his actions fell within the measures recommended by the United Nations, and reminded "all members of the United Nations" to "consider carefully the consequences of this latest aggression in Korea" and that America "will continue to uphold the rule of law."