As a result of World War II, Korea was liberated from Japan and divided in two: Communist North Korea (supported by the Soviet Union), and South Korea (supported by the US).
In 1950, Kim II Sung, the leader of North Korea, invaded South Korea in order to unify both countries under his command. In response to this invasion, President Truman ordered the US forces to aid its ally and reject North Korea advances.
Even when the conflict resulted on military stalemate, the United States proved the ideals of the Truman Doctrine by controlling communist invasion in the context of Cold War.
