Four decades on, the trauma of the war between the US and Vietnam is beginning to fade, and the two countries are undergoing a transformation in relations.
"We struggled 1,000 years against the Chinese, 100 years against the French and 20 years against the Americans. It is time to think of the future," said a ministry of foreign affairs spokesman in Hanoi recently.
Many Vietnamese are too young to remember the horrors of war
That future evidently assumes an ever-closer relationship between the old enemies, Vietnam and the US.
It has been an extraordinary transformation, to see the coming together of two nations so deeply divided by history, ideology and culture.
To understand how it has happened, the part played by demographics is important.
Seventy per cent of the population of Vietnam was born since 1975 and has no memory of the war.
When I spoke to students at the Polytechnic University in Hanoi, they had no interest in discussing what they call "the American War".
They wanted to talk about the future, not to dwell on the past.
They would like, if at all possible, to study in the US because they admire its educational opportunities and - significantly - its "freedom".
Two young women spoke admiringly of former president Bill Clinton but made very long faces at the mention of President George W Bush: "He makes too many wars around the world," they felt.
Many Americans, including war veterans, are visiting Vietnam as tourists and they may well find themselves talking to their former enemies, the Viet Cong (VC), who successfully infiltrated every corner of South Vietnamese life, including the armed services.
One of those Viet Cong is Nguyen Thanh Trung.
Nguyen Thanh Trung secretly joined the Viet Cong in 1969
When Trung was a boy, his father, a Viet Cong guerrilla, was shot and killed and his body mutilated by the South Vietnamese army.
Trung came to terms with his father's death but never with the desecration.
For 12 years he planned his revenge.
In 1969 he enlisted in South Vietnam's air force. The day before, he had secretly joined the Viet Cong.
He was sent to the United States and trained as a fighter pilot.
A few weeks before Saigon fell to Communist forces in April 1975, Trung made off with his F-5 aircraft and dropped two bombs through the roof of the Presidential Palace.
His revenge was complete. But by that time, he says, it no longer mattered.
The most important thing was to put an end to the fighting.
Now he is working hard to improve relations with the US and he is in a very good position to do just that.
Trung is now chief pilot and a vice president of Vietnam Airlines and he proudly told me that next year it starts direct flights to the US.
It is, he says, not only commercially important, but it marks an important milestone in improving US/Vietnam relations.
Another former Viet Cong activist is now formally charged with improving relations with the United States.
Ambassador Ton-Nu-Thi Ninh is unlikely revolutionary material.
This is the opportunity of centuries, of millennia and we've got to grab it
Madame Ninh, National Assembly member
She was born into an aristocratic, Mandarin family and given a French education.
It was in Paris in the 1960s that she was swept up in the radical student movement and recruited by the VC.
On returning to Saigon, she became Professor of English at Saigon University while working undercover to bring the Communists to power.
She is now a member of the National Assembly and vice-chair of the Foreign Affairs Committee.
Like many Vietnamese, Madame Ninh distinguishes between the American people, whom she likes and the American Government, which she sometimes finds difficult.
"The [American] officials... are lacking some sensitivity... I think that Vietnam is showing a lot of self-restraint and that is not acknowledged enough by the officials," she said.
But for Vietnam to prosper, it is very important, she said, to have good relations with the US.
"For a country [like Vietnam] that wants to escape from poverty... to build its place in the sun, in peace, this is the opportunity of centuries, of millennia and we've got to grab it."
Businessman Kien Thanh Bui made a similar point.
Mr Bui is a Vietnamese American, an expert on banking and insurance, who has been advising the Hanoi Government on building a market economy.
He said it is in the interests of the US and Vietnam that commercial ties continue to grow.
The volume of trade already tops $8bn a year and the US is a substantial investor in Vietnam.
One of those investors is Henry Nguyen.
Henry's father is a civil engineer who worked for the Americans and who escaped to the US, just before Saigon fell in 1975.
Henry was a tiny baby at the time and grew up "an all-American kid".
But in his 20s, he was drawn back to his roots and now runs a major venture capital business in Vietnam.
Both the US and Vietnam, he said, are drawn together by trade but there are also very clear political and security issues relating to China.
"Vietnam... doesn't want too much influence from China and, at the same time, tries to balance out with the US and vice-versa," he said.
What with trade, geo-politics, kinship, tourism and the generation gap, the direction of Vietnam/ US relations seems irreversible.
BBC Radio 4's Crossing Continents will be broadcast on Thursday, 13 July 2006, at 1102 BST.
The programme will be repeated on Monday, 17 July at 2102 BST.