The old Ho Chi Minh trail passes right by Bui Thi Duyen's doorstep in the hamlet of Doi. The hamlet, quiet and isolated, is of no consequence today, but during what the Vietnamese call the "American War," many thousands of northern soldiers knew Doi, 50 miles south of Hanoi, as an overnight stop on their perilous journey to the southern battlefields. The camouflaged network of footpaths and roads they traveled was the world's most dangerous route. One North Vietnamese soldier counted 24 ways you could die on it: malaria and dysentery could ravage you; U.S. aerial bombardments could disintegrate you; tigers could eat you; snakes could poison you; floods and landslides could wash you away. Sheer exhaustion took its toll as well.

When the war ended in 1975, much of the Ho Chi Minh Trail was abandoned. The jungle pushed in to reclaim the supply depots, rickety bridges and earthen bunkers that stretched more than a thousand miles from a gorge known as Heaven's Gate outside Hanoi to the approaches of Saigon. Hamlets like Doi were left to languish, so remote they weren't even on maps. That North Vietnam had been able to build the trail—and keep it open in the face of relentless American attacks—was considered one of the great feats of warfare. It was like Hannibal crossing the Alps or General Washington the Delaware—an impossibility that became possible and thus changed the course of history.

I met Duyen when I returned to Vietnam last May to see what was left of the trail that bore the name of the country's revolutionary leader. She was sitting under a blue tarpaulin, trying to fan away the breathless heat and hoping to sell a few sweet potatoes and half a dozen heads of lettuce spread out on a makeshift bench. At 74, her memory of the war remained crystal clear. "There was not a day without famine then," she said. "We had to farm at night because of the bombing. Then we'd go up in the mountains and eat tree roots." What food the villagers had—even their prized piglets—they gave to the soldiers who trekked through Doi, pushing bicycles laden with ammunition or stooped under the weight of rice, salt, medicine and weapons. She called them the "Hanoi men," but in reality many were no more than boys.

These days, though, Duyen has things other than the war on her mind. With Vietnam's economy booming, she wonders if she should cut her ties with tradition and swap the family's 7-year-old water buffalo for a new Chinese-made motor scooter. It would be an even trade; both are worth about $500. She also wonders what impact Vietnam's most ambitious postwar public works project will have on Doi. "Without that road, we have no future," she says.

The project, started in 2000 and scheduled to take 20 years to complete, is turning much of the old trail into the Ho Chi Minh Highway, a paved multilane artery that will eventually run 1,980 miles from the Chinese border to the tip of the Mekong Delta. The transformation of trail to highway struck me as an apt metaphor for Vietnam's own journey from war to peace, especially since many of the young workers building the new road are the sons and daughters of soldiers who fought, and often died, on the Ho Chi Minh Trail.

The old infiltration and supply route—which the Vietnamese call Truong Son Road, after the nearby mountain range—wasn't a single trail at all. It was a maze of 12,000 miles of trails, roads and bypasses that threaded through eastern Laos and northeastern Cambodia and crisscrossed Vietnam. Between 1959 and 1975 an estimated two million soldiers and laborers from the Communist North traversed it, intent on fulfilling Ho Chi Minh's dream to defeat South Vietnam's U.S.-backed government and reunite Vietnam. Before leaving Hanoi and other northern cities, some soldiers got tattoos that proclaimed: "Born in the North to die in the South."

During the war, which I covered for United Press International in the late 1960s, the Ho Chi Minh Trail had an aura of foreboding mystery. I could not imagine what it looked like or who trekked down it. I assumed I would never know. Then in 1997, I moved to Hanoi—the "enemy capital," I used to call it in my wartime dispatches—as a correspondent for the Los Angeles Times. Almost every male I met over 50 had been on the trail, and during my four years in Hanoi and on subsequent trips to Vietnam, I filled several notebooks with their stories. They invited me into their homes, eager to talk, and not once was I received with anything but friendship. I came to realize that the Vietnamese had put the war behind them, even as many Americans still struggled with its legacy.

Trong Thanh was one of those who greeted me—at the door of his home, tucked deep in a Hanoi alleyway, with a cup of green tea in hand. One of North Vietnam's most celebrated photographers, he had spent four years documenting life on the Ho Chi Minh Trail and had toured the United States with his pictures in 1991. The images spoke of the emotions of war more than the chaos of combat: a North Vietnamese soldier sharing his canteen with a wounded enemy from the South; a moment of tenderness between a teenage soldier and a nurse who looked no older than 15; three adolescent privates with faint smiles and arms over one another's shoulders, heading off on a mission from which they knew they would not return. "After taking their picture, I had to turn away and weep," Thanh said.

Thanh, whom I interviewed in 2000, six months before his death, pulled out boxes of photos, and soon the pictures were spread across the floor and over the furniture. The faces of the youthful soldiers stayed with me for a long time—their clear, steady eyes, the unblemished complexions and cheeks without whiskers, the expressions reflecting fear and determination. Their destiny was to walk down the Ho Chi Minh Trail. It would be left to their children to be the first generation in more than a hundred years not to know the sounds of battle or the bondage of foreign domination.

"It used to take two or three months for a letter from your family to reach you on the front," Thanh said. "But those were our happiest times on Truong Son, when we got mail from home. We'd read the letters aloud to each other. Pretty soon one soldier would laugh over something in a letter, then everyone would laugh. Then you'd feel so guilty for being happy, you'd cry, and the whole forest would echo with falling tears."

Storm clouds were rolling in from Laos the morning last May that I left Hanoi with a driver and an interpreter, bound for the former demilitarized zone that once separated North and South Vietnam at the 17th parallel. The bustling capital gave way to rice paddies and fields of corn. An elegantly dressed young woman went by, a live pig strapped to her motor scooter's rear rack. A small red flag of Communist Vietnam fluttered from her handlebar—its five-pointed star representing workers, farmers, soldiers, intellectuals and traders.

"Where's the road south?" my driver shouted to a farmer as we passed through Hoa Lac, 45 minutes southwest of Hanoi. "You're on it," came the reply. So this was it: the start of the new Ho Chi Minh Highway and below it, now covered by pavement, the legendary trail still celebrated in karaoke bars with songs of separation and hardship. No historical plaque marked the spot. There was only a blue-lettered sign: "Ensuring public safety makes everyone happy."

The new highway, which will not stray into Laos or Cambodia as the old trail did, will open up Vietnam's remote western interior to development. Environmentalists fear this will threaten wildlife and flora in national preserves and give access to illegal loggers and poachers. Anthropologists worry about its effect on the minority mountain tribes, some of whom fought on the side of South Vietnam and the United States. Health experts say truck stops along the route could attract prostitutes and spread AIDS, which took the lives of 13,000 Vietnamese in 2005, the last year for which figures are available. And some economists believe the $2.6 billion for the project would be better spent upgrading Route 1, the country's other north-south highway, which runs down the eastern seaboard, or on building schools and hospitals.

But government planners insist the highway will be an economic boon and attract large numbers of tourists. "We cut through the Truong Son jungles for national salvation. Now we cut through the Truong Son jungles for national industrialization and modernization," former Prime Minister Vo Van Kiet remarked, as construction began in April 2000. Most of the 865-mile stretch from Hanoi to Kon Tum in the Central Highlands has been completed. Traffic is light, and hotels, gas stations or rest stops are few.

"It may sound strange, but although it was a terrible time, my four years on Truong Son was a very beautiful period in my life," said Le Minh Khue, who defied her parents and at age 15 joined a youth volunteer brigade on the trail, filling bomb craters, digging bunkers, burying corpses and ending each day covered head to toe with so much mud and dirt that the girls called each other "black demons."

Khue, a writer whose short stories about the war have been translated into four languages, went on: "There was great love between us. It was a fast, passionate love, carefree and selfless, but without that kind of love, people could not survive. They [the soldiers] all looked so handsome and brave. We lived together in fire and smoke, slept in bunkers and caves. Yet we shared so much and believed so deeply in our cause that in my heart I felt completely happy.

"I'll tell you how it was," she continued. "One day I went out with my unit to collect rice. We came upon a mother and two children with no food. They were very hungry. We offered to give her some of our rice, and she refused. 'That rice,' she said, 'is for my husband who is on the battlefield.' That attitude was everywhere. But it's not there anymore. Today people care about themselves, not each other."

The road was born May 19, 1959—Ho Chi Minh's 69th birthday—when Hanoi's Communist leadership decided, in violation of the Geneva Accords that divided Vietnam in 1954, to conduct an insurgency against the South. Col. Vo Bam, a logistics specialist who had fought against the French colonial army in the 1950s, was given command of a new engineer unit, regiment 559. Its 500 troops adopted the motto, "Blood may flow, but the road will not stop." The trail they started building was so secret that their commanders told them to avoid clashes with the enemy, "to cook without smoke, and speak without making noise." When they had to cross a dirt road near a village, they would lay a canvas over it so as to leave no footprints.

Before long there were thousands of soldiers and laborers on the trail, hidden under triple-canopy jungle and camouflage nets. They built trellises for plants to grow over, scaled cliffs with bamboo ladders, set up depots to store rice and ammunition. Villagers donated doors and wooden beds to reinforce the crude road that slowly pushed south. Porters stuffed bicycle tires with rags because their cargo was so great—up to 300 pounds. There were makeshift hospitals and rest stops with hammocks.

The United States began sustained bombing of the Ho Chi Minh Trail in 1965. B-52 bombers dropped loads of 750-pound bombs in 30 seconds to cut a swath through the forests the length of 12 football fields. The monster Daisy Cutter bomb could carve out a crater 300 feet in diameter. That same year, a young doctor, Pham Quang Huy, kissed his wife of two months goodbye in Dong Hoi and headed down the trail. He carried the traditional farewell gift that wartime brides and girlfriends gave their departing soldiers—a white handkerchief with his wife's initials embroidered in one corner. So many young men never returned that handkerchiefs became a symbol of grieving and parting throughout Vietnam. Huy did not see his home again—or even leave the trail—for ten years. His daily ration was one bowl of rice and one cigarette. In all the time he was away, he and his wife were able to exchange only seven or eight letters.

"The soldiers became my family," Huy, 74 and retired from his civilian medical practice, told me. "The most terrible time for us was the B-52 carpet-bombing. And the artillery shelling from the coast. It was like being in a volcano. We'd bury the dead and draw a map of the grave site, so their families could find it. Our equipment was very simple. We had morphine but had to be very economical in its use. Soldiers begged me to cut off an arm or leg, thinking that would end their pain. I'd tell them, 'You should try to forget the pain. You must recover to finish your job. Make Uncle Ho proud of you.' "

Trying to stop the infiltration of men and supplies into South Vietnam, the United States bombed the Ho Chi Minh Trail for eight years, setting forests ablaze, triggering landslides, denuding jungles with chemicals and building Special Forces outposts along the Laotian border. The Americans seeded clouds to induce rain and floods, launched laser-guided bombs to create choke points and trap truck convoys, and parachuted sensors that burrowed into the ground like bamboo sprouts, relaying data on movement back to the U.S. surveillance base at Nakhon Phanom in Thailand for evaluation. But work never stopped, and year after year infiltration into the South increased, from 1,800 soldiers in 1959 to 12,000 in 1964 to over 80,000 in 1968.

After each aerial attack, hordes of soldiers and volunteers scurried to repair the damage, filling craters, creating bypasses and deliberately building crude bridges just beneath the surface of river water to avoid aerial detection. By 1975, truck convoys could make the trip from the North to the southern battlefields in a week—a journey that had once taken soldiers and porters six months on foot. Antiaircraft artillery sites lined the road; a fuel line paralleled it. The trail made the difference between war and peace, victory and defeat, but it took a terrible toll. Upward of 30,000 North Vietnamese are believed to have perished on it. Military historian Peter Macdonald figured that for every soldier the United States killed on the trail, it dropped, on average, 300 bombs (costing a total of $140,000).

As my interpreter and I headed south along the new highway, there was nothing beyond tidy, manicured military cemeteries to remind us that a war had ever been fought here. Forests have grown back, villages have been rebuilt, downed fighter bombers have long since been stripped and sold for scrap metal by scavengers. The mostly deserted two-lane highway swept through the mountains north of Khe Sanh in a series of switchbacks. In the distance flames leapt from ridge to ridge, as they had after B-52 strikes. But now the fires are caused by illegal slash-and-burn logging. Occasionally young men on shiny new motor scooters raced past us. Few wore helmets. Later I read in the Vietnam News that 12,000 Vietnamese were killed in traffic accidents in 2006, more than died in any single year on the Ho Chi Minh Trail during the war. Peace, like war, has its price.

Sometimes we drove for an hour or more without seeing a person, vehicle or village. The road climbed higher and higher. In the valleys and gorges the ribbon of road flowed south through a parasol of high trees. What a lonely and beautiful place, I thought. A new steel bridge spanned a fast-flowing stream; next to it stood a crumbling wooden bridge over which no soldier's sandals had trod in 30 years. We passed a cluster of tents with laundry drying on a line. It was 8 p.m. Twenty or so bare-chested young men were still at work, laying stone for a drainage ditch.

In Dong Ha, a shabby town once home to a division of U.S. Marines, we checked into the Phung Hoang Hotel. A sign in the lobby inexplicably warned in English, "Keep things in order, keep silent and follow instruction of hotel staff." A segment of the twisting mountain highway we had just driven over had been built by a local construction company owned by an entrepreneur named Nguyen Phi Hung. The site where his 73-man crew worked was so remote and rugged, he said, the earth so soft and the jungles so thick that completing just four miles of highway had taken two years.

Hung had advertised in the newspapers for "strong, single, young men" and warned them that the job would be tough. They would stay in the jungle for two years, except for a few days off over the annual Tet holiday. There were unexploded bombs to disarm and bodies of North Vietnamese soldiers—seven, it turned out—to be buried. The site was out of cellphone range, and there was no town within a week's walk. Stream water had to be tested before drinking to ensure it contained no chemicals dropped by American planes. Landslides posed a constant threat; one took the life of Hung's youngest brother. For all this there was handsome compensation—a $130 a month salary, more than a college-educated teacher could earn.

"When we gathered the first day, I told everyone life would be hard like it was on the Truong Son Road, except no one would be bombing them," Hung said. "I told them, 'Your fathers and grandfathers sacrificed on this road. Now it is your turn to contribute. Your fathers contributed blood. You must contribute sweat.' I remember they stood there quietly and nodded. They understood what I was saying."

I left the Ho Chi Minh Highway at Khe Sanh and followed Route 9—"Ambush Alley," as Marines there called it—toward the Ben Hai River, which divided the two Vietnams until Saigon fell in 1975. Looking out the window of my SUV, I was reminded of one of the last promises Ho Chi Minh made before his death: "We will rebuild our land ten times more beautiful." If by beautiful he meant prosperous and peaceful, his pledge was being fulfilled.

Factories and seafood-processing plants were going up. Roads built by the colonial French were being straightened and repaved. In the towns, privately owned shops had sprung up along the main streets, and intersections were clogged with the motorcycles of families who couldn't afford a pair of shoes two decades ago. I stopped at a school. In the fourth-grade history class a teacher was using PowerPoint to explain how Vietnam had outsmarted and defeated China in a war a thousand years ago. The students, sons and daughters of farmers, were dressed in spotlessly clean white shirts and blouses, red ties, blue pants and skirts. They greeted me in unison, "Good morning and welcome, sir." A generation ago they would have been studying Russian as a second language. Today it is English.

Since the early 1990s, when the government decided profit was no longer a dirty word and, like China, opened its economy to private investment, Vietnam's poverty rate has dropped from nearly 60 percent to less than 20 percent. Tourism has boomed, foreign investment has poured in and the United States has become Vietnam's largest export market. A stock market is flourishing. Vietnam still wears the cloak of communism, but today the blood of free-market reform fills its capitalistic heart.

Two-thirds of Vietnam's 85 million people were born since 1975. For them, the war is ancient history. But for their parents, the trail and its rebirth as a highway are potent symbols of sacrifice and loss, of endurance and patience—a symbol as enduring as the beaches of Normandy are to Allied veterans of World War II.

"My greatest pride is to have followed my father's generation and worked on the highway," said Nguyen Thi Tinh, a senior planner in the Ministry of Transportation, who knows every turn and twist of the new road. Her father, a professional singer and saxophone player, was killed in a bombing attack on the trail while entertaining soldiers in 1966. "I'm embarrassed to say this, but if I'd had a gun at the time, I would have killed all Americans," she said. "Then I realized that the same thing that happened to my family happened to American families, that if I had lost my son and I was an American, I would have hated the Vietnamese. So I buried my hatred. That is the past now."

We talked for an hour, just the two of us in her office. She told me how in 1969 she had gone—during a bombing pause—to the battlefield where her father died. With the help of soldiers, she dug up his grave; his remains were wrapped in plastic. Among the bones was a tattered wallet containing an old picture of him with her—his only daughter. She brought him home to Quang Binh Province for a proper Buddhist burial. As I got up to leave, she said, "Wait. I want to sing you a song I wrote." She opened a notebook. She locked her eyes with mine, placed a hand on my forearm and her soprano voice filled the room.

"My dear, go with me to visit green Truong Son.
We will go on a historical road that has been changed day by day.
My dear, sing with me about Truong Son, the road of the future,
The road that bears the name of our Uncle Ho.
Forever sing about Truong Son, the road of love and pride."

In a few years the highway will reach Ho Chi Minh City, formerly known as Saigon, then push on into the Mekong Delta. I left my interpreter and driver in Hue and caught a Vietnam Airlines flight to Ho Chi Minh City. April 1975 and Saigon's last days flashed to mind. Thirty-two years ago, I had spread out a map on the bed in my hotel near South Vietnam's parliament. Each night I had marked the advancing locations of North Vietnam's 12 divisions as they swept down the Ho Chi Minh Trail to the city's doorstep. The end of the war was at hand and it would come amid chaos but with surprisingly little bloodshed.

"I was 12 miles north of Saigon with the 2nd Division before the final advance," said Tran Dau, a former North Vietnamese officer living in Ho Chi Minh City. "We could see the lights of the city at night. When we came in, I was surprised how modern and prosperous it was. We had been in the forests so long that anyplace with pavement would have seemed like Paris."

Dau knew how harsh Hanoi had been toward the South in the nightmarish 15 years following reunification. Southerners by the hundreds of thousands were sent to re-education camps or economic zones and forced to surrender their property and swallow rigid communist ideology. Hanoi's mismanagement brought near-famine, international isolation and poverty to all but the Communist Party elite. In 1978, Vietnam invaded Cambodia, overthrowing the regime of dictator and mass murderer Pol Pot, then, in 1979, fought off invading Chinese troops in a month-long border war. Vietnam stayed in Cambodia until 1989.

The former colonel shook his head at the memory of what many Vietnamese call the "Dark Years." Did he encounter any animosity as a victorious northern soldier who had taken up residency in the defeated South?

He paused and shook his head. "People in Saigon don't care anymore if their neighbor fought for the South or the North," he said. "It's just a matter of history."

David Lamb, a writer based in Virginia, is the author of Vietnam, Now: A Reporter Returns.
Mark Leong, an American photographer living in Beijing, has covered Asia since 1989.