The Vietnam War After World War II ended, the world was polarized. The Communist World, was composed of the Soviet Union and its satellites and allies, and the powers of the Western world, was composed of the United States and its allies. They have different political systems and opposite ideologies. Both of them want to expand their influence in the world. So, they clashed with each other. Since World War II just ended, both of their powers greatly weakened by the war, so they did not dare to launch a large-scale war between each other. Therefore, Indochina became a battlefield and symbol under the background of the Cold War. United States intervened in Indochina between 1941 and 1975. At the same time, the United States wanted to win over the support of France, and strengthen the cooperation with the Europe, so that he can contain the Soviet Union better. In addition, Indochina's strategic location was very important to the United States. Under the background of the Cold War, the military, economic and political environment had changed in the world. In military, Korean War, Vietnam war, Cuban Missile Crisis happened in that period and the “Berlin Wall” appeared in the Germany. In economics, an important measure was Marshall Plan. And in political environment, both of them engaged in a wide range of spying activities. During the Cold War, started from Harry Truman, all American leaders hope to contain communism from all over the world. But when Richard Nixon administration won the election in 1968, he adjusted the policy to the Soviet Union, China and Vietnam. In addition, with the president administration changed, strategies and tactics were shifted over time. At that period, the constant frictions between the two nations were in many aspects. In political system, US government was decentralized and liberal, but Soviet government was centralized and authoritarian. In ideologies, US was foremost capitalist power, but Soviet was the major power that claimed himself to be Marxist. The US government tried to stop communism spreading throughout the world. With Chinese Communists defeated the Kuomintang in the civil war and Kuomintang's troops retreated to the island of Taiwan, US government felt he lost a large part of the forces in Asia. So, as Viet Winh waged guerilla war to gain independence from France and received aid from China at the same time, the US government felt stress and panic. They thought the Indochina war was no longer a colonial war between colony and colonial country, but the struggle between communist forces and non-communist forces. So US government thought he should take all practicable measures to prevent further communist expansion in Southeast Asia. In addition, after withdrawal of Japanese, France attempted to restore colonial rule in Indochina. However, Vietnamese resisted this action. During the same period, U.S created military alliance (NATO) in 1948 with most European nations not under Soviet control. Therefore, U.S. urgently wanted to win over France and get Europe’s support to restrict the expansion of the Soviet Union. Despite U.S. was willing to finance its military power to France, France still could not retain its hold in Indochina, French defeated by Vo Nguyen Giap and withdrew from Vietnam in 1954. After the withdrawal of France, U.S also supported Ngo Dinh Diem as ruler in the south. It sent billions of U.S dollars and military advisers to prop up his government to antagonize Ho Chi Minh and his Viet Cong in the north. The most important reason about the intervention of U.S was Indochina's strategic location. In politics, U.S had lost China in Asia. If it also lost Indochina, that means Soviet power will be extended. In economics, Southeast Asia owns a large population and it was rich in natural resources. So if U.S lost this area, that means U.S and his Europe allies lost an important supplier of market and