how long did the Vietnam War last?
Since there was no declaration of the war, exact dates are sketchy. However, it is now widely accepted that the Vietnam War started on November 1, 1955 and lasted until April 30, 1975, which is roughly 20 years, or 19 years, 180 days to be precise.
American involvement in Vietnam began as early as in 1950 when President Truman sent military advisors to aid the French in the First Indochina War while its direct involvement started from 1964 until 1973. The Vietnam War is still commonly considered as the longest war that the U.S. has ever involved in its entire history.
As for the Vietnamese, they experienced the First Indochina War (also known as the Indochina War or Anti-French War) against the French from December 19, 1946 until August 1, 1954 right before the Vietnam War (Second Indochina War). So for them it was nearly 30 years altogether.
It is worth noticing that Vietnam invaded Cambodia in the wake of the Vietnam War to overthrow the genocidal Khmer Rouge regime in the war which would last until September 1989. In return, the People’s Republic of China (PRC) who were the Khmer Rouge’s political ally, also launched a short punitive invasion of Vietnam in February –March 1979 so as to “teach them a lesson”for their invasion of Cambodia.