After World War II, Stalin did not remove his troops from Eastern Europe as he pledged he would in the Yalta Agreement. Instead, he setup puppet governments which did exactly as Mother Russia stated. To protect its interests for national security, the American Dream, and the belief that all people should have the right to a democratic life, complete with liberty, equality, and a representative government. Also playing a large part in Cold War tensions was the US interest in protecting its profitable foreign markets. The spread of communism challenged every one of these US aims, and therefore the US became convinced it had to stop this spread.
The deliberate opposition to the spread of communism to capital countries is known as containment, which the US adopted in the late 1940s. The US believed it must do everything in its power to uphold containment and save its peoples way of life. Another theory that soon surfaced that was related to the containment theory was the domino theory, which stated that as one small country fell to communism, surrounding small countries would also fall to communism rapidly. In the spirit of containment, strongly supported by President Harry Truman, was the main driving force behind the Korean War.
Along with containment as a force was American Pride. After World War II and after Japanese occupation, Soviet troops moved in to North Korea, and the US moved in to South Korea. Each setup and supported its own government, and each government wanted unification on its own terms. The North Koreans were the ones to strike first, and the situation quickly involved US troops. Although originally winning the war easily, Gen. Macarthur ignored Chinese warnings and advanced further north. The Chinese entered the war in October 1950, and forced the UN forces back below the 38th parallel.
Both held their grounds fiercely for the next two years, the UN forces driven by containment and the Communist forces driven by the ideal of global communism, until finally in 1953 a truce was signed in which the country was left divided exactly where it was before the war, along the 38th parallel. The Korean War caused much frustration in the home fronts, where people wondered why 54,000 US men had died and many more were wounded for virtually no gains. Many people also questioned the countrys determination in enforcing containment. This led to a much larger defense budget, as NSC-68 had outlined.
Just as the Korean War was coming to an end, another was brewing 2,000 miles to the south. Vietnam long controlled by France, had also been occupied by the Japanese during World War II. France was determined to win back its empire after the war and was backed strongly by the British. The US was influenced by the British and also supported the French. Ho Chi Minh, the rebel leader of Vietnam, had other plans. He was indomitable about getting independence for Vietnam, and would settle for nothing less. The US backed France strongly economically in its war in Indochina; however, France was defeated by the Vietnamese at Dein Bien Phu.
At a peace conference later in Geneva drew a dividing line, similar to the 38th parallel in Korea, in Vietnam at the 17th parallel. To the north was a communist government under the control of Ho Chi Minh, to the south was an anti-communist regime supported by the US. It was decided that elections would be held in 1956 to unify the country. Eisenhower as well as Kennedy, were strong believers in the domino theory, and were adamant that South Korea would not be lost to the communists. To them, the matter was not only of national safety and protection, but also of American Pride.
The US and South Korea did not commit to the elections in 1956, due to fears that Ho Chi Minh would win. Instead, the US sent troops to South Korea under the guise of advisors. There were 675 advisors at the beginning of the struggle, by the end of 1963, the were more than 16,000 US advisors in South Vietnam. After years of escalation and military setbacks like the Tet offensive, poor US puppet governments in South Vietnam, and protests and upheaval in the home front, the US abandoned Vietnam in what is considered the first war lost by the US.
The policy of containment was a successful one. Communist has all but been cleared from the surface of the earth. The USSR fell more than ten years ago, and China will soon allow free trade. The role of US intervention and influence on the spread of communism and its eventual outcome is debatable. Communism may still be in the same boat as it is in now if the US had not fought the Korean and Vietnam Wars, and the domino theory did not prove true as Cambodia, Laos, Thailand remained capitalistic.