After WW2, the most powerful countries in the world were the US and the Soviet Union, who soon became bitter rivals.
The Soviet Union began invading Europe and destroyed their democratic governments, replacing them with communist governments. In the same year, 1949, China also became a communist nation. After the civil war the Communists drove the non-communists from Mainland China, causing the US to become concerned, as they believed that the spread of communism was a threat to America. This was a major role in the US government's decision to send troops to Vietnam. Vietnam was the most important of France's colonies, and after Japan's surrender in 1945 France tried to regain control of Vietnam, however many of the Vietnamese resisted and in 1946 Ho Chi Minh declared Vietnam an independent country. War broke out in 1946 because France refused to accept their declaration of independence and both sides expected aid from the US but since Ho Chi Minh was a Communist and had the backing of the Soviet Union, the US backed France. By 1956, US was concerned that communism was becoming too strong in Asia and the president at this time was afraid that all of SE Asia would fall to communism like a row of dominoes.
He also feared that if communists took over Vietnam its neighbors soon would, too, so he supported South Vietnam whereas China, wanting communism to spread through Asia, backed North Vietnam. Soon the North Vietnamese began fighting with the South Vietnamese. The Vietcong used tactics of guerilla warfare, a type of fighting in which small groups of rebel soldiers make surprise attacks against government soldiers and enemy bases. As the war progressed, The media changed as a result of the Vietnam War. At the beginning of the conflict, most people in the media supported the war effort, but over time it became clear that there was a gap between what the government was saying and what was really happening in Vietnam..