World War II was global war, especially involving Europe’s colonial empires in Asia. By the mid twentieth century East Asia started developing economically and politically to challenge European supremacy.
United States was worried about the further spread of Communism and Soviet power into East Asia. It decided to provide Japan with economic aid to help it revive. As a result, Japan’s prosperity and stability rapidly recovered, making it a strong ally and trading partner for the United States.
China’s civil war between Communists (led by Mao Zedong) and Nationalists (led by Chiang Kai-shek) resumed after Japan’s defeat. Communists backed by Soviets emerged victorious in 1949.
Americans and Soviets partitioned Korea after the war at the thirty-eighth parallel. In 1950, North Korean forces invaded South Korea and overran most of it. United Nations passed a resolution calling for an international force to stop the North Koreans. American troops led by General Douglas Macarthur drove North Korean back north. Chinese forces entered North Korea and drove them back south and stalemate resulted in ceasefire at the thirty-eighth parallel. The Korean War contained the spread of Communism, but at the cost of a divided Korea and the loss of millions of lives and huge material damage.