The Tet offensive marked the moment when what had been seen as a relatively manageable overseas conflict involving the United States turned into something much more messy.
The assaults launched by the Viet Cong against the South Vietnamese and their US military allies in early 1968 - coinciding with the Tet festival, or lunar new year -- were a military fiasco. But the size of the offensive, the dramatic increase in US troop numbers it triggered, and the consequent loss of life on all sides, weighed heavily on US public opinion and led to Lyndon Johnson's refusal to seek re-election in that year's presidential race.
The Viet Cong attacked on six specific targets in Saigon, including the American embassy, the National Broadcasting Station and the office of President Nguyen Van Thieu. None was successful, but television images of US General William Westmoreland in front of a devastated embassy strewn with bodies had a jolting effect on public perceptions at home.
The offensive also involved a long, draining battle for the Khe Sanh airstrip, used as a US Marine base south of the demilitarised zone separating North and South Vietnam. Khe Sanh became a symbol of the war's futility, abandoned as it was in June 1968, deemed to be of no strategic worth.
The Tet offensive gave so much life to the anti-war Democratic presidential candidate, Eugene McCarthy, that he came close to scoring an upset victory over the President in the New Hampshire primary. That inspired Bobby Kennedy to enter the race, and prompted Mr Johnson to withdraw.
Perhaps the iconic moment was in late February when Walter Cronkite, the revered CBS Evening News anchor, visited Vietnam and told his viewers the US was "mired in a stalemate" and needed to get out.Reuse content