In addition one of the assumptions in the USA of the early Cold War was that the SU controlled all communist movements and parties throughout the world and that any manifestation of communist aggression must have been inspired and assisted by Moscow. So strong was the American belief in the existence of a monolithic communist block, that the NKs were assumed to have been acting on orders from Stalin. In consequence, the USA intervened in the Korean war, not only to defend the independence of SK but also to deny the SU a victory in the Cold War.
Moreover, the USA intervened in the Korean war because of domestic pressure placed on Truman and the Democratic party within the US government. Truman and the Democratic party were accused of being too soft on communism by their opponents the republican party. The two major cold war events in 1949 provided the republicans with the perfect arguments to exploit the weaknesses of the democrats. In august 1949 the SU successfully tested its atomic bomb, which the Americans didn’t expect to happen until the 1950s and therefore brought the US atomic monopoly to an end. Soon after in October 1949 Mao Zedongs communists emerged victorious from the Chinese civil war. This was perceived by the republican as the fall of china and the Truman administrations failure to be tough on communism.
The domestic position for Truman worsened when the republican senator Joe McCarthy began to make accusations of communist sympathisers and supporters within the state department. Although he had no real proof Americans believed him, as McCarthyism provided the only simple and persuasive explanation for why the communist powers appeared to be winning the cold war. Therefore the US government’s internal political difficulties made a firm response to the NK attack on SK inevitable.
The cold was a war of ideologies. USA felt threatened by communism and thought communist SU was out to destroy democracy and capitalism. Therefore was prepared to defend free countries from aggressive communist countries. However the US supported Syngman Rhee who’s regime was hardly a model of freedom and democracy. But the US government was willing to overlook this fact because Rhee was very anti-communist. The US also supported undemocratic and corrupt countries in the late 1940’s such as Greece and Turkey by providing them with $400 million of Marshall aid.
US went to war in Korea to protect their economic interests in Japan. The K war made it justifiable for the US to retain their military bases in Japan. Furthermore J was identified by Kennan as one of the five military-industrial world powers which must remain within US orbit. Anchoring J to the US was the cornerstone of the strategy of containment in Asia. This was why the US supported J with aid of $500 million a year in an attempt to rebuild their shattered economy. A revived J would provide a bulwark against the SU and contribute to the economic revival of the newly independent states in South and North west Asia. Therefore the US was keen to build up J rather than SK as a major power and military ally to assist the US in the Pacific region.
The US used the UN to justify its intervention in the K war. The UN passed a resolution within a month of the war and clarified the reasons for its involvement. It said that the armed attack on SK by NK was a breach of peace. The resolution called for member states to assist SK to defend against armed attack and restore international peace. Therefore by using the UN the US government was able to gain support of its allies. The US was able to use the UN to ratify its own decisions and involvement in the conflict as SU was absent from the meeting having withdrawn form the security council because the UN had given Chinas seat to Taiwan instead of the Peoples Republic of China.
Due to the fact that korea was a peninsula it was thought that the war would be winnable with low costs as it would be easy to project Naval and aerial power. Trumans airforce advisers had convinced him that Americas bombers would be able to stop the aggression in K by destroying the communist supply lines. Therefore Truman believed it was possible to defeat NK without any commitment of American ground troops.
In conclusion the Korean war was another course of the Cold war in which the two superpowers fought to show that their way of life was better than the other. The underlying reason for the American involvement in the K war was due to containment which meant that the US would do anything to prevent anymore countries becoming communist. Korea was therefore a way of sending a message to the SU that the US would not stand by idly and watch the world fall into communist hands.