Many US soldiers who fought in Vietnam will remember Hanoi Hannah, the silky-voiced communist radio correspondent who urged young American GIs to stop fighting and go home.

She is the most famous of dozens of Vietnamese journalists drafted by the communists to help the war effort, which ended 40 years ago this month with the fall of the city then known as Saigon.

In daily broadcasts from the northern capital Hanoi, Hannah would play music by Joan Baez and Bob Dylan, announce the names of American troops killed in fighting, and read clippings from US newspapers about anti-war protests.

"Nothing is more confused than to be ordered into a war to die or to be maimed for life without the faintest idea of what's going on," Hannah, whose real name is Trinh Thi Ngo, said on air, reading from a script whose message was tightly controlled by the communist authorities.

Ngo joined the state-run Voice of Vietnam as a young woman and her near-perfect English was seen by the state's propaganda masters as a way to connect with US servicemen.

Now a frail octogenarian, she lives in southern Ho Chi Minh City -- renamed after Vietnam's independence hero after the 1975 victory -- but declined AFP interview requests on health grounds.

"She helped US soldiers understand what was going on," said Tran Duc Nuoi, a former top editor at Voice of Vietnam.

"Her broadcasts shook American soldiers... because of Hanoi Hannah's voice, some soldiers started opposing the illogical war and put down their weapons," he added.

Propaganda was essential to both sides' wartime strategies.

The US dropped billions of anti-communist leaflets over Vietnam. But it could not fully control the western press, and their raw, powerful coverage of Vietnam is credited with swaying US public opinion on the conflict.

Meanwhile, Hanoi tightly controlled the domestic flow of information, highlighting only its successes and American failures, not the enormous losses it was suffering.

But observers say the impact of efforts to demoralise Americans -- including through Hanoi Hannah's broadcasts -- have been overblown.

"I don't think many GI's actually listened to her, much less were influenced by what she said. They knew it was all propaganda," said Carl Robinson, a journalist who covered the war for the Associated Press, adding US forces preferred listening to their army's own radio network.

Because of a tendency to over-exaggerate, the communist journalists also lost credibility, he said.

"So when they did have something serious to say like the My Lai massacre, no one believed them," Robinson added, of the infamous March 1968 slaughter of Vietnamese villagers by American soldiers.

- 'Profound hatred' for US -

Unlike the foreign press, which in the main tried to provide balance, Vietnamese correspondents had a clear bias.

"If you saw Americans walking down the streets carrying the severed head of your comrade would you not hate them?" said famed Vietnamese war photographer Dinh Quang Thanh.

It was their "duty" to highlight communist victories and help the war effort, said Thanh, who photographed communist soldiers entering Saigon's Independence Palace, to bring the war to an end on April 30, 1975.

"We couldn't stand these people who brought bombs and shells into our country to kill," he said.

At least 2.5 million soldiers from Vietnam's communist North and US-allied South died in the conflict alongside three million civilians, according to official figures.

On the American side, more than 58,000 soldiers lost their lives, while some estimates say more Vietnam veterans committed suicide after the war than died in fighting -- although the figures are disputed.

Vietnamese reporters faced the same -- if not worse -- dangers as their foreign colleagues, who have been lionised since the war for their powerful coverage.

Images such as AP photographer Nick Ut's Pulitzer-winning shot of a fleeing, napalm-burned girl, and Hugh Van Es's photograph of desperate Vietnamese trying to board a helicopter from a rooftop in downtown Saigon, have come to define the war.

Some 200 Vietnamese correspondents -- who lived alongside regular army units -- were killed during the conflict.

"I didn't have time to think about my family, to wonder whether I'd survive and make it home... you were surrounded by blood and fire," said photographer Thanh.

"We had no time to feel afraid. I just thought about whether I could do my job -- take the photos to show our victory," Thanh, now 80, told AFP.

While Vietnamese reporters working for the communist side were certainly less balanced in their reporting than the foreign press, their images were still powerful, according to photographer Tim Page, who covered the war for UPI.

"The problem that the great frames taken by the photographers on the 'other side' is that they never got to see the light of day in the west," Page, co-author of a book of images by foreign and Vietnamese journalists killed in the war, told AFP.

- Journalism 'came of age' -

During the conflict, Vietnamese journalism "came of age," Page said, and the legacy lives on with many young photographers still busy documenting "a society, economy and politic that is rapidly evolving."

As was the case during the war, journalists now must strictly follow the Vietnamese Communist Party line -- all media in Vietnam, ruled by the party with an iron fist since reunification in 1975, is state-run.

But many chafe against these restrictions and readers increasingly prefer to side-step state-run media and find their news on blogs or social media.

And despite the restrictions, the quality of the photojournalism in particular remains high.

"In today's Vietnam you will find some of the world's best unsung shooters," said Page.