The United Nations authorized its members to send troops to Korea. They passed a resolution in the United Nations, a peace-keeping organization formed at the end of World War II, condemning North Korean action and demanding that the communist army pull back. The United States and other Western nations determined to resist communist efforts to expand. For the next few months, they pushed the small South Korean army south to a port city of Pusan. These fears were confirmed in June, 1950, when the army of communist-led North Korea crossed the border and invaded South Korea. Americans were worried that communists were planning aggression against other nations in eastern Asia. All of mainland China, then home to a half-billion people, came under communist control while the pro-Western army fled to the nearby island of Taiwan. In 1949, a civil war in China ended with a victory for the communists. The Soviet Union claimed that communism would one day rule the world, but Western democracies were determined to prevent that. However, sometimes smaller conflicts broke out between nations backed by the two sides. It was called the 'cold' war because while both the Soviets and the West (the United States, Great Britain, and western Europe) maintained large armies, no direct fighting broke out between the two sides. Korea was part of a world-wide struggle called the Cold War. The army of North Korea, however, was larger, better equipped and better trained. Both the government in the north and the government in the south claimed that it alone was the valid government of all of Korea. The small peninsula of Korea was divided between a communist government, supported by the Soviet Union in the north, and a government supported by the United States in the south.

In eastern Asia, the war left many of the nations that Japan had invaded and occupied unstable.

In 1945, World War II came to an end with the surrender of Germany and Japan.

Why the cold war is called cold