What role did Korea play in the Cold War?

In the era of the Cold War, the two superpowers - the
United States and Soviet Union - refrained from attacking each other directly for fear
of a large scale nuclear war. Instead, they chose to fight over the soil of a different
country/countries. Korea provided one such
opportunity.

North and South Korea were influenced by
Communism and capitalism respectively, and thus served as host to American and Russian
philosophies. When enmity between the two nations (North Korea- the communist, and South
Korea- the capitalist) increased, the US and the Soviet Union participated on their
behalf and entered the Korean War. Ultimately, China was involved in the war as well;
and unfortunately the conflict between North and South Korea has not been solved even
today. 

Thus, Korea played the role of providing a reason
and resources for the two Cold War enemies to fight each other.