二战后美国的对外政策

Engagement and Expansion
The fall of the Berlin Wall in 1989, the change of color of the Eastern European countries and the disintegration of the Soviet Union at the end of 1991 radically changed the balance of power in the world. The Clinton Administration made national security, economic prosperity and promotion of democracy the three pillars of American foreign policy. Its national strategy was engagement and expansion, which means the United States will take a more active part in world affairs and will more actively promote Clinton market economy and American style democracy in the world.
The Arms Race
In order to break the monopoly of atomic weapons by the USA, the Soviet Union had long been working on the building of the bomb .In 1949,the Soviet Union detonated its first atomic device. The USA had its first test of the hydrogen bomb in 1952,and the Soviet Union followed in 1953.In 1957,the Soviet Union launched two sputniks into the orbit showing they had the vehicle to carry the bombs to the United States.
On one occasion during Cold War period, the USA and the Soviet Union were on the brink of a nuclear war. This occasion was the Cuban Missile Crisis in 1962.However, the Soviet Union flinched at last. In Asia, the containment policy was directed against the People’s Republic of China. The frozen relationship did not thaw until president Nixon visited China in 1972.
Conclusion
During 1945-1991 , the basic goal of the foreign policy of the USA is to contain Soviet expansion and to bring about change in Soviet political system. After 1991, the basic goal is to maintain American domination in the world as long as possible and to remake the world in American image. Whatever policy the United States has pursued in the past half a century and more, it is based on the US analysis of the world situation and on the determination of American core interests.
The Containment Policy
Truman
Apart from the arms race, the USA put into effect the containment policy in The late 1940s.In 1948 president Truman put forward the Truman Doctrine, which is generally regarded as the formal Nixon announcement of containment. During this time, the USA fight two wars in Asia: the Korean War and the Vietnam War. Those two wars greatly weakened the United States. The Nixon Doctrine made clear that the United States no longer planned to fight a ground war in Asia but would provide nuclear protection to its allies in the region and give military and economic support to countries fighting against domestic communism.
In Europe, as a result of the Cold War, the German was separating East and West German. The East German built a wall which was called Berlin Wall, it was the symbol of the Cold War.
Unilateralism and Faith in Military Strength
When George W. Bush became the president in 2001,he and his top advisers pursued a strategy that has significantly changed some of the principles that have been practiced in American foreign policy for years. This strategy has two prominent elements :unilateralism and faith in military strength. If they think any international agreement is not in line with American national interests, they will not hesitate to discard it. On March 20,2003,the USA launched large-scale air attacks on Iraq without United Nation authorization, which was aimed at the oil. It protects its interests.
POST-WWⅡ AMERICAN FOREIGN POLICY

The Beginning of the Cold War
By the end of the WW-Ⅱ,the United States not only emerged unscathed but also became the strongest country in the world. The planners of the USA were visualizing a Pax Americana. They wanted a world order dominated by the USA, a world market which was free and open to American goods and services and more and more countries modeling on American institution and values. In pursuing this goal, the USA determined resistance from the Soviet Union. However, the Soviet Union had a big lost in WW-Ⅱ，it wanted to keep what it had got in the war. Gradually, the USA and the SU fell apart, the Cold War began to unfold in Europe.
Eisenhower
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Kennedy
The United States under the Eisenhower Administration and the Kennedy Administration stepped up research and production of nuclear weapons and the carrying vehicles. By the 1980s,the two countries had more than 50 000 nuclear weapons that could kill the people in the world many times.
Later ,when the Soviet Union Ronald Reagan Stepped up its race in nuclear force, American strategy shifted to the balance of terror — mutual assured deterrence .When Ronald Reagan became the president in1982,he wanted to reverse the situation. He initiated the Star Wars project. He planned to drag the Soviet Union into another round of arms race, which he was sure that the Soviet Union would end in bankruptcy.