Hello, David Wilson here for About.com. I'm an historian and a teacher of U.S. and World History. In today's topic, we're going to be discussing the Cold War between the United States and the Soviet Union.As World War II ended, and with the Soviet Union refusing to pull out of the occupied countries of Eastern Europe, the Cold War between the United States and the USSR was underway. Among the Cold War issues foremost on the minds of the American government was the expansion of the Soviet Union.In an address before congress in 1947, President Harry Truman said: “It must be the policy of the United States to support free peoples who are resisting attempted subjugation by outside pressures.” This became known as the Truman Doctrine; as a strategy, it would be referred to as Containment. The effort to put this Containment strategy into effect resulted in the United States taking part in a massive arms build-up, fueled in part by a 1950 National Security Council Report which recommended huge increases in defense spending.This, coupled with the Soviets successful testing of an atomic bomb in 1949, gave birth to what was referred to as the arms race, whereby both countries continued to build massive stockpiles of ever more destructive weapons.Beginning in the late 1950s, the Cold War competition between the United States and the Soviet Union spilled into space exploration. Dubbed “The Space Race,” it was an effort to see who could send a man past the bounds of Earth, and further. Americans were sent a shocking blow when the Soviets successfully launched the first man-made satellite into Earth’s orbit. Sputnik, as it was called, prompted a huge response, which included the launching of a U.S.-built satellite called Explorer I, and the creation of NASA, both which occurred in 1958. The Soviets then launched the first man into space, Yuri Gagarin, in April of 1961. However, the Space Race was effectively won by the United States by successfully landing men on the moon, and returning them safely to Earth in July of 1969.The Cold War also had some very hot spots, where proxy wars were fought between the U.S. and U.S.S.R. Korea was the first of these hot spots, with the Soviet-backed North Koreans attacking the U.S.-backed South Koreans in June of 1950. The war ended in a stalemate in 1953 after three years of brutal fighting.The next hot spot to occur in the Cold War was the 1961 U.S.-led Cuban Bay of Pigs Invasion, which failed to topple the Communist government of Cuba. The following year, the Cuban Missile Crisis exploded, which nearly drew the world into a nuclear war as the United States Navy blockaded the Cuban islands from the Soviets.In the 1960s, the United States' support of the South Vietnamese against the Communist North Vietnamese in the Vietnam War led to a costly protracted conflict that cost the lives of tens of thousands of U.S. troops. American combat operations in Vietnam ended in 1973 and the South Vietnamese capital of Saigon fell to the North two years later. Under the Reagan Administration, Cold War tensions rose again as it became the Reagan Doctrine to support forces around the world who were resisting Communism.At the same time, to counter severe economic problems in the U.S.S.R., Premier Gorbachev introduced many policies that encouraged political openness and economic reforms. These policies began to tear at the fabric of the Soviet Union, pushing the Eastern Block countries under their Communist rule into revolution. Lastly, in November of 1989, the Berlin Wall was finally destroyed, and by 1991, the once mighty Soviet Union was no more; hence, the Cold War was over.Thanks for watching. To learn more, visit us on the web at about.com.