The Role of the US
The US helped South Korea a lot during the Korean War. As a part of the UN Security Council, they contributed the most. Without them, South Korea would have had a greater chance at losing the war. More than 55,000 American troops were lost in the war. There were many things that pressured Truman into entering the war :
"The decision to intervene in Korea grew out of the tense atmosphere that characterized Cold War politics. On the eve of the North Korean invasion, a number of events had made Truman anxious. The Soviet Union exploded an atomic bomb in 1949, ending the United States' monopoly on the weapon. . . 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 Truman administration also faced internal criticism regarding its commitment to anticommunism at home. Republican Senator Joseph McCarthy of Wisconsin had recently begun his infamous hunt for communists within the U. S. Government. Although McCarthy was just warming up, the recent trials of Alger Hiss and others for espionage left the Truman administration apprehensive about its anticommunist credentials. Truman and his advisors found themselves under increased domestic pressure not to appear "soft" on communism abroad. Thus, when North Korean troops invaded the South, the Truman administration seized upon the opportunity to defend a noncommunist government from invasion by communist troops. Determined not to "lose" another country to communism, and interested in shoring up its anticommunist credentials, the Truman administration found itself defending a nation a world away from U.S. soil. Yet Truman's response was not merely a response to internal pressure. The invasion of South Korea made Truman genuinely fearful that the Soviet Union and China intended to expand the sphere of communism throughout Asia."
-- from www.archieves.gov ( Teaching With Documents: The United States Enters the Korean Conflict )
"The decision to intervene in Korea grew out of the tense atmosphere that characterized Cold War politics. On the eve of the North Korean invasion, a number of events had made Truman anxious. The Soviet Union exploded an atomic bomb in 1949, ending the United States' monopoly on the weapon. . . 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 Truman administration also faced internal criticism regarding its commitment to anticommunism at home. Republican Senator Joseph McCarthy of Wisconsin had recently begun his infamous hunt for communists within the U. S. Government. Although McCarthy was just warming up, the recent trials of Alger Hiss and others for espionage left the Truman administration apprehensive about its anticommunist credentials. Truman and his advisors found themselves under increased domestic pressure not to appear "soft" on communism abroad. Thus, when North Korean troops invaded the South, the Truman administration seized upon the opportunity to defend a noncommunist government from invasion by communist troops. Determined not to "lose" another country to communism, and interested in shoring up its anticommunist credentials, the Truman administration found itself defending a nation a world away from U.S. soil. Yet Truman's response was not merely a response to internal pressure. The invasion of South Korea made Truman genuinely fearful that the Soviet Union and China intended to expand the sphere of communism throughout Asia."
-- from www.archieves.gov ( Teaching With Documents: The United States Enters the Korean Conflict )
Implications :
I support the US for going in to help South Korea because like them, they believed that communism was wrong. They made a huge difference in the war as they supplied South Korea with many troops and managed to push back North Korea. However, I think there was a point where they should have held their ground and stopped pushing North Korea back because that triggered China to intervene into the war and they lost many troops because of that and the war was prolonged.