More than 30 years after the Vietnam War ended, the Veterans' Memorial in Washington DC remains a place of pilgrimage and remembrance.
By Jonathan Marcus
BBC diplomatic correspondent
The US president initially denied any parallels between the two wars
The memorial, a long black granite wall set into a grassy bank, carries the names of more than 58,000 Americans killed or missing in the conflict.
This compares with some 4,000 combat deaths in Iraq.
But, inevitably, comparisons are being made between the two conflicts.
In some ways the similarities are obvious.
There is the sense of a war entered into under false pretences.
There is the feeling of being bogged down in a conflict with no obvious end in sight.
And, just as in Vietnam, there is the fear that the very nature of the conflict has been misunderstood.
For a long time President George Bush refused to accept that there was any comparison between Iraq and Vietnam.
In April 2004, for example, he insisted that any analogy between the two conflicts was "false" and that making such comparisons sent the wrong message both to US troops and to enemies of the US.
But in August of this year Mr Bush changed his tune.
Speaking to a veterans' organisation in Kansas City he said one unmistakeable legacy of Vietnam was that "the price of America's withdrawal was paid by millions of innocent citizens".
Their agony, he said, "would add to our vocabulary new terms like 'boat-people', 're-education camps' and 'killing fields'".
Robert Dallek, one of the country's pre-eminent historians, told me that when he listened to Mr Bush's speech he thought it "an abuse of history".
Mr Bush, he said, had "avoided using the Vietnam analogy for a very long time because he didn't want to invoke memories of a failed war".
But now he was seeking to use Vietnam against critics of the Iraq war by saying that if the US rushed to leave Iraq, the consequences could be similar to the mayhem that afflicted Cambodia and Vietnam.
This, Mr Dallek said, was simply "a false analogy".
Leslie Gelb put it rather nicely. A Pentagon official during the Vietnam era and now president emeritus of the Council on Foreign Relations in New York, he told me that Iraq is not Vietnam but that "history is intent on harnessing them together".
Vietnam, he says, "is the most significant historical comparison to what the United States is going through now, so it was inevitable that this would be the touchstone."
So what then was the real impact of the Vietnam War on the US?
The conflict in South-East Asia came at a time of much greater turmoil - the struggle for civil rights, for women's rights and for the creation of a more open, liberal society.
It had a dramatic impact on US politics.
The crunch came amid violent scenes at the Democratic Party's convention in Chicago during the election year of 1968.
Veteran political analyst David Gergen says, "Vietnam effectively splintered the Democrats; destroying the consensus within the party on international affairs".
The Red Arrow Diner is a popular spot for presidential candidates
For a time the Democrats moved to the left and, David Gergen says, they paid a huge price at the polls.
"That sense of weakness in the Democratic Party helped to elect Richard Nixon, helped to elect Ronald Reagan, helped to elect George H W Bush and indeed George W Bush," he said.
When you hear questions raised even today by Republican candidates wondering if the Democrats can be trusted on national security issues, well that is one of the legacies of the Vietnam era.
Vietnam certainly changed US politics. Could the war in Iraq have a similar effect?
New 'military mums'
I travelled around the state of New Hampshire in early November, sitting in on a town hall meeting with Republican candidate John McCain and stopping off at the famous Red Arrow Diner in the former mill town of Manchester, a favourite destination for political hopefuls on the campaign trail.
Iraq was certainly one of the chief issues on people's minds, though domestic concerns like healthcare also figured prominently.
At the Red Arrow Diner I spoke to the manager Elaine Boule.
Her brother-in-law was killed in Iraq and she told me that while she had generally voted Republican she was now leaning towards the Democrats - perhaps a candidate like Hillary Clinton - who she thought might be strong on defence.
She is typical of a whole new category of swing voters, what New Hampshire political analyst Jennifer Donahue described to me as "military mums", women with connections to the military whose Republican convictions can no longer be counted upon.
The next presidential election is still a year or so away.
But David Gergen believes that Iraq is going to remain the single most important issue in the campaign.
Anger at the war in Iraq will have a greater impact on foreign relations
"So many people are angry," he says.
The country is split into about 40% Democrats and 40% Republicans. But the 20% of independents look to be shifting towards the Democrats and that, he says, "will be enough to swing the election".
The experts agree on one thing though: Iraq is not set to have anything like as much impact on political life in the US as the Vietnam conflict.
"Vietnam is like a dark shadow over our politics," Kurt Campbell of the Center for a New American Security told me.
But he added that internationally the US recovered very quickly after Vietnam.
"I think in Iraq it is going to be precisely the opposite," he went on.
"The domestic political consequences seem grave now but I think we'll recover reasonably rapidly from those.
"It's going to be in the region and internationally where the consequences of Iraq are likely to be much darker and much more troublesome for this and the next generation of American politicians and diplomats."
The first programme of the Seeing Iraq: Thinking Vietnam two-part series will be broadcast on Monday 26 November at 0800 GMT on the BBC World Service. To listen again click on the link at the top of this page.