The Korean War was the first major proxy war of the Cold War and a significant test of the Truman Doctrine in action. It also signified the rapid deterioration in the relationship between the United States and the Soviet Union. Each superpower saw the other's policy in Korea as imperialistic and a threat to their own ideology.
President Truman had serious anxieties over the Soviet's role in the region. The fall of China to Communism in 1948 and its new alliance with the Soviet Union threatened to spread Communism throughout East Asia. Truman, already committed to containment and facing criticism for "losing China," wanted to act quickly. When fighting broke out in Korea, Truman sent in troops under the auspices of NATO and the UN. To Stalin, this appeared to be a threat to Soviet hegemony in the region.
Prior to the conflict in Korea, most American policymakers viewed the Soviet Union as a cautious imperial power. Even with the first Soviet tests of atomic weapons in 1949, many in the US...
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