The Korean War was the USA’s first major military venture following the Second World War. From 1950 to 1953 the USA alongside many allies fought under the auspices of the United Nations to resist aggression and then to roll back the encroachment of communism in the Korean Peninsula. The USA could justify their claims to be fighting in the interests of ‘collective security’ in resisting aggression from North Korea, this enabled the close cooperation of the USA with the UN, keen to avoid the taint of failure attributed to its predecessor the League of Nations.

As a willing participant in the United Nations, the USA was showing its resolve not to remain isolated and to confront potential threats to global security. The USA was helped by the boycott of the UN by the Soviets following the failure to recognise the government of Chairman Mao, the People’s Republic of China in 1949. Without the spoiling tactics of the Soviet veto, the USA had much freer rein to take the UN along with it in taking decisive action. The cloak of the United Nations and the support of the World community lent greater legitimacy to US actions and the moral sense of mission for Truman.

Korea had been divided after the war into two zones of occupation divided by the 38th parallel. In the North under the supervision of the occupying Soviets, a communist government was established by Kim Il Sung while in the South a pro-American regime was led by Syngman Rhee. The withdrawal of the occupying forces of the USSR and USA was meant to be followed by free elections leading to a unified government. Both factions dug their heels in with the tacit support of their superpower backers.

Border skirmishes were common and it could be argued that the invasion by the North in June 1950 was little more than what the South had already been doing. The US considered this part of the continuing push toward communist World domination. To the United States this action was part of the wider Soviet conspiracy to expand the frontier of communism; after the Soviet domination of Eastern Europe, the Berlin blockade and the fall of China, it seemed part of the pattern which threatened US interests on a global scale.

The recent development of the Soviet A-Bomb further increased the sense in Washington that Stalin was wanting to flex his muscle. There is no substantial evidence that Moscow supported and approved of Kim Il Sung’s actions, this is clearly indicated in the limited military support provided to North Korea by the Soviets. The perception of Soviet malfeasance spurred the US into taking more decisive action.

The US military establishment and defence department pounced on Korea as the means to expand US ‘peacetime’ defence spending, the proposals of NSC-68 to increase spending on nuclear and conventional forces had a limited impact on Truman and Congress until Korea provided the pretext for escalating US military commitment. Korea also came at an appropriate time for politicians keen to play on the ‘Red Scare’ like Senator McCarthy, in an atmosphere of intimidation, it was vital for the US government to be seen to be acting tough in the face of communism.

It is uncertain whether the US intervened in Korea in order to contain communist North Korean expansion or to eradicate communism from the peninsula, a policy of ‘rollback’. Some could even argue that the aim was to open a front in Korea which would see the overthrow of communism in China and a restoration of pro-US authority. It is here where US interests have diverged from those of the UN. The United Nations gave military command in Korea to the US President, who, in turn, gave it to General Douglas MacArthur.

The initial US/UN was a clear success, having advanced to the Pusan perimeter, MacArthur’s bravura Inchon landings sent the North Koreans into disarray. By October 1950 the North had been pushed back beyond the 38th parallel. Here the US could have stopped in successfully restoring Syngman Rhee to South Korea, but the decision was taken to push North up to the Chinese border on the Yalu River. MacArthur’s success forced China to take action against the US/UN force, convinced it sought to destroy it.

The Chinese ‘volunteers’ pushed the US back south, below the line of Seoul. The situation became so dire for the US army that it seriously contemplated the use of nuclear weapons against China. This could have seen the Soviet Union take a decisive involvement and would have escalated the Korean War into a World War. Disagreements over the conduct of the war led to the sacking of MacArthur by Truman, under the more cautious Matthew Ridgeway the 38th parallel again became the dividing line between North and South Korea.

Stalemate led to another two years of fighting without significant shifts in the front line, by 1953 the change of President and the death of Stalin precipitated the Peace at Panmunjom. The US had grown weary of their involvement, unsure of what their role or purpose had been. US involvement in Korea stemmed from the desire to contain communism, had non-communist aggression been involved then it is inconceivable for Truman to take the action that he did. The involvement of the UN did little more than provide a legitimate pretext for US action and allow it to show moral leadership.

US concerns were not about the inhabitants of Seoul or Pyongyang but rather in the interests of preventing, what it feared was the inexorable, expansion of communism in Asia. Once containment had been achieved then the US sought to push the frontiers of communism back in response to domestic pressures and military interests. The failure to strike this decisive blow against Korea, China or the Soviet Union then led to disenchantment and US desire to disentangle itself from its commitment. These were the reasons why the USA intervened in Korea 1950 to 1953.