With most wars, it is fairly easy to pinpoint beginning and ending dates. This is not so much the case with the Vietnam War. One well-known television documentary called this war the “10,000 Day War,” thus implying that it lasted nearly 30 years. Other sources have it lasting different lengths of time.
In one sense, the US was involved in the Vietnam War from 1954 to 1973. Vietnam had been a French colony before WWII. During that war, it was occupied by Japan. After the war, the French tried to reoccupy the territory but were resisted by Vietnamese nationalists/communists led by Ho Chi Minh. The French lost their war and withdrew in 1954. From then on, the US was closely involved in trying to prevent Ho and his people from gaining control of all of Vietnam. The country of Vietnam was split into North Vietnam, controlled by Ho and his movement and South Vietnam, controlled by a non-communist government supported by the US. The US gradually became more involved in military operations. The peak of US involvement was from 1965 through 1970, with all American troops removed in 1973.
This war was significant in US history for two main reasons. First, it is the only war that the US ever clearly lost. Second, and more importantly, it was tremendously divisive. Americans were badly split over whether the country should even be involved in Vietnam. The war led to huge protests and helped cause a cultural split between traditional elements of US society and more liberal elements. This split lasts to the present. The war continues to haunt us because it implies that our power is limited and because of the fissures that it helped to cause and expose in our society.