Almost half a century has passed since the end of this war in 1975, but we still talk about the Vietnam War as a way of commemorating the soldiers who died.
According to thoughtco.com, Beginning in the mid-1950s, the American foreign policy establishment tended to view the situation in Southeast Asia in terms of the Domino Theory. They feared that, if Indochina were to fall into the hands of the communists, who were fighting the French, the expansion of communism across Asia might be out of control. The Domino Theory suggested that other nations throughout Asia would become satellites of either the Soviet Union or Communist China, much like nations in Eastern Europe had come under Soviet domination.
After the World War 2, from 1949, fear of domestic communists gripped America. The country spent much of the 1950s under the influence of the Red Scare, led by the virulently anti-communist Senator Joseph McCarthy. McCarthy saw communists everywhere in America and encouraged an atmosphere of hysteria and distrust.

Internationally, following World War II, country after country in Eastern Europe had fallen under communist rule, as had China, and the trend was spreading to other nations in Latin America, Africa, and Asia as well. The U.S. felt that it was losing the Cold War and needed to “contain” communism.
It was against this backdrop that the first U.S. military advisers were sent to help the French battle the communists of Northern Vietnam in 1950. That same year, the Korean War began, pitting Communist North Korean and Chinese forces against the U.S. and its UN allies.
The French were fighting in Vietnam to maintain their colonial power and to regain their national pride after the humiliation of World War II. The U.S. government had an interest in the conflict in Indochina from the end of World War II until the mid-1950s. And in support of France, on May 1, 1950, the President of the United States quickly approved a $10 million grant to France, marking a major decision for the United States to become involved in the Indochina War. Thus, from 1945 to 1950, the United States implemented a policy to support the French recapture Indochina, to extinguish the communist fire in Indochina. This also demonstrated an American obsession with the Domino effect, fearing that Communism would dominate the world.
Throughout the early 1950s, the Viet Minh forces made significant gains. In May 1954, the French suffered a military defeat at Dien Bien Phu and negotiations began to end the conflict. Following the French withdrawal from Indochina, the solution put in place established a communist government in North Vietnam and a democratic government in South Vietnam. The Americans began supporting the South Vietnamese with political and military advisers in the late 1950s.
The French failure at Dien Bien Phu created a great deal of concern for the US global strategy. The American rulers have recognized Vietnam as the most important “outpost” in the US global strategy in Southeast Asia. Therefore, the US took steps to help Ngo Dinh Diem establish a pro-American government in South Vietnam, to realize America’s strategic goals. On July 7, 1954, the United States brought Ngo Dinh Diem, a long time American raised, to be Prime Minister of the South Vietnamese government. This was an important move, a prelude to direct US intervention in Vietnam.