The Vietnam War (1954–1975) was a conflict between North Vietnam and South Vietnam, in which the United States allied with South Vietnam. At the time, the Vietnam War (called the American War in Vietnam) was the longest war in American history. It has given its name to a generation in the United States, and politicians have fought over its meaning, lessons, and legacies in every presidential election since 1964, even before the United States officially sent ground troops there. To the present day, the Vietnam War and the United States’ involvement in it remain controversial. This entry discusses the controversy amid a historical look at the progression of the war, from its origins to its end and aftermath.