Image copyright Charles Fox

More than 40 years after the end of the Vietnam war, dozens of ageing former American soldiers have gone back to the country to live. Some had difficulty adapting to civilian life in the US. Others have gone back in the hope of atoning for wrongs they believe were committed during the war.

At the foot of one of Da Nang's Marble Mountains women with rice hats walk around selling souvenirs. A lift takes tourists to the top, where on one side they look out over the countryside of central Vietnam, on the other the South China Sea.

In 1968 David Edward Clark was camped behind these mountains, but then it was impossible to climb them, the 66-year-old says. Anyone doing so would be a sitting duck for the Vietcong camped nearby.

"We even had the rule that you would never leave the camp without a gun," says Clark. "So I walked around with an M16 all day. And I put that thing in the face of every Vietnamese I encountered. Men, women and children. I wanted them to be scared of me. That would give me a bigger chance to survive."

Image copyright Charles Fox

Forty years later Clark came back to Vietnam, this time not to fight Communists, but to build a new life. Clark is one of about 100 American veterans, maybe more, who have established themselves in Vietnam. Many of them live in and around Da Nang, the city where the US had its busiest military airfield during the war and where the first American troops arrived in 1965.

Back in the US, after the war, not a day went by without thinking of Vietnam, says Clark, who hides his eyes behind a big pair of sunglasses. "I often woke up, bathing in sweat. I saw people when they weren't there. Once I got up in the middle of the night, planning to place ambushes around my house, because I thought the Vietcong were coming to get me. The only way I could escape from these memories was by getting drunk. So I drank way, way too much."

I was so heavily brainwashed that before I went to war I wanted to kill Communists Richard Parker, Veteran

In 2007, Clark finally managed to take a step back. For this he had go back to the mountain that separated his platoon from the enemy and for the first time in his life he climbed all the way up. "On the top I had a feeling of peace I never had before. There were no more bombs, there was no more fighting, there were no more jet fighters flying over. Then I realised the war is over."

It's estimated that tens of thousands of veterans have returned to Vietnam since the 1990s, mostly for short visits to the places where they once served. Decades after the fall of Saigon (now Ho Chi Minh City) many former soldiers still wonder why they were fighting.

That goes for Richard Parker, also 66, who says he "lost the plot" after Vietnam, and for 20 years led a life of alcohol, drugs and sex.

Image copyright Charles Fox

"I was a vagabond who worked in restaurants and who went from town to town. It didn't matter to me if I was dead or alive," he says.

I have the feeling that we need to restore some things... we have done so many stupid things here Larry Vetter, Veteran

Memories of destruction and death in Vietnam continuously haunted him. "I was so heavily brainwashed that before I went to war I wanted to kill Communists. But when I left Vietnam, I loved the people there," he says. "How were they dangerous? The only thing they wanted to do was grow rice and make babies."

For many years Parker suffered from post-traumatic stress disorder, a disease that today affects 11% of Vietnam veterans. Tens of thousands have committed suicide.

For Parker the only way to put his demons to rest was to return to Vietnam. "Here I found, more or less, peace with myself. Sometimes I go to a place where we used to fight. What was chaos and destruction at the time, is now a hopeful place full of life."

Another veteran, Larry Vetter works for Child of War Vietnam, a website that aims to tell people about the legacy of the Vietnam War. Both American and Vietnamese flags hang in his spacious house. Above the sofa there is a wedding portrait - this summer, the 73-year-old married his Vietnamese girlfriend, Doan Ha.

Image copyright Charles Fox

When Vetter came to Da Nang in November 2012 he only intended to stay three months to help a family care for two sick boys apparently suffering from the effects of Agent Orange, a chemical herbicide used by the US military to kill trees and shrubs, which is still causing cancer, deformities and paralysis today.

Back in the US everything felt meaningless - I was like a piece of the puzzle that didn't fit in Chas Lehman, Veteran

"I have the feeling that we need to restore some things," says Vetter, who is known to his friends as Captain Larry. "The US government refuses to do that, so I'm here to do my part."

It was partly a sense of guilt that led Vetter to stay in Vietnam after the three months were over.

"There's a closet in my head that I don't want to open, because I fear of what comes out of it. I don't know exactly what's in there, but every now and then the door opens a bit and I get bad dreams. Maybe this closet is the reason I'm in Vietnam. We have done so many stupid things here."

Chas Lehman, a man in his 70s with a white beard and dark sunglasses, describes his return to Vietnam as the will of God. It was conversion to Christianity, he says, that saved him from falling into a black hole of depression, disillusion and post-traumatic stress disorder.

Image copyright Charles Fox

"When I was sent to Vietnam, the mission seemed simple: I had to prevent the free South Vietnam from becoming a slave of the Communist North. But from the time I arrived on Vietnamese soil, I knew this wasn't right and that I had to get out of here," he says. "Back in the US everything felt meaningless. I was like a piece of the puzzle that didn't fit in. Then Jesus saved me and gave meaning to my life."

I know this is where I have to be - the war is over, and I will die here David Edward Clark, Veteran

Together with other volunteers Lehman distributes food, drinks, clothing and blankets to needy minority groups in Vietnam's Central Highlands. On a single trip they can assist 65 to 300 families. "During the war, I felt sorry for the people in Vietnam, but I couldn't trust them. Now I feel affection for them," he says.

Returning to Vietnam is a way to end frozen memories, says Richard Parker. "As long as you don't return, you will remember Vietnam as the country of the war."

Although he sometimes teaches English, most of the former vagabond's days are a simple pattern of reading, walking, talking with friends and enjoying Vietnamese cuisine.

Image copyright Charles Fox

His eyes light up when he explains how Vietnam has made him a happy man again. He laughs a lot these days. "And the Vietnamese show respect for me, even more respect than I get as a veteran in the US," he says.

David Clark would like to see more veterans coming back to Vietnam. He himself came back several times after his first trip. During a motor bike journey from north of the country to the south something else happened that he would never have expected in 1968 - he fell in love with a Vietnamese woman. They married two years ago.

Image copyright Charles Fox

The veteran takes a deep breath. He takes off his sunglasses, wipes away a tear. His voice breaks. "I used to think the Vietnamese were the dirtiest, lowest scumbags in the world. But now I feel blessed for living here. I know this is where I have to be. The war is over, and I will die here."

Image copyright Charles Fox

In his living room Larry Vetter shows me a picture on his laptop. There he is, a young twenty-something man in a helicopter, at the end of the 1960s. Beneath him is the Vietnamese jungle, next to him a soldier with a machine gun. "After the war I had a lot of questions, but there was no-one who gave me answers," says Vetter. "So I went to study myself. And the more I read, the less I understood about why we were sent to Vietnam. I found out how much they lied to us and thought to myself: 'If I were Vietnamese, I would have fought with the Vietcong.'"

From the kitchen his wife, Doan Ha, looks at him lovingly. Captain Larry may be much older and may have memories of Vietnam that she will never fully understand, but she loves him. "He has a good heart," she says. "Not just for me, but for everyone."

Image copyright Charles Fox

More from the Magazine

A tall, thin American wearing a straw hat wanders through the narrow streets of Ho Chi Minh City, clutching a photo album. At his side is a Vietnamese interpreter and fixer, Hung Phan, who has helped dozens of former American soldiers locate their long-lost children over the last 20 years. His latest client, the American under the straw hat, is Jerry Quinn. He has come to Vietnam to find his son.

Read: A US soldier searches for his Vietnamese son

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