The longest war in US history took place in Vietnam during the Cold War. The United States' involvement in the Vietnam War began when the Vietnamese were fighting the French for independence. Prior to U.S. involvement, France had attempted to rule Vietnam as one of its colonies, but after years of war with rebels and communists, France could no longer resist. The United States feared the spread of communism and considered itself a democratic superpower, and therefore felt morally obligated to rise up and fight against communism in France's place. Vietnam was later divided into North and South Vietnam at the Geneva Conference, originally designed to end the Franco-Vietnamese War. North Vietnam was ruled by communists and supported by China and Russia. South Vietnam was then supported exclusively by the United States. The United States intervened in Vietnam for four main reasons: it wanted to contain communism, prevent the domino effect, support a very weak South Vietnam, and get retaliation for being attacked. After seeing China fall to communism in 1949, Lyndon Johnson did not want the same thing to happen in Vietnam. He decided that the United States must fight to contain communism in Vietnam and prevent the domino theory. The domino theory simply stated that if one country fell to communism, neighboring countries would soon follow suit, falling like a domino. Essentially, the Americans believed that if South Vietnam fell, Laos, Cambodia, and Thailand would follow. Furthermore, South Vietnam could not resist the Vietcong alone because they were too weak and ill-equipped to fight. The United States believed that with good government, on a large scale and... middle of paper... much larger and also costing the lives of many civilians, they considered it a necessary evil. Many lives were lost, but they emerged free and independent. The United States eventually withdrew from the war. The Vietcong were protecting their way of life and their choice of government from an aggressor who sought to prevent them from gaining independence. Although American troops had all the advantages in terms of military might, the Viet Cong had the will to fight with what little they had and made the most of the basic weapons they were given. American troops in this war were on average much younger and much less willing to fight. The more lives the Viet Cong lost, the more determined they were to win. Instead, the more American lives lost, the more they wanted to pack their bags and go home. And that's exactly what they did.