Halfway to Georgetown, John Kerry stopped the car. It was 1993, his first time driving Teresa Heinz home, but first he had something to show her. Kerry led his date along a path on the Mall, to the V-shaped slabs of black granite of the Vietnam Veterans Memorial. He walked her through the night, without saying a word.

"Every now and then he'd point to a name on the wall. Dickie [Pershing] was one. He went to all his friends, I saw all his friends," Teresa Heinz Kerry, now Kerry's wife, recalled in an interview. Kerry walked her to the Lincoln Memorial, and then back to the Wall before speaking again.

"He said, 'Look at that wall, everybody on that wall died after we knew that war was a mistake.' And he was angry, quietly angry, seething angry, and we left. It was a visit to the promise of Lincoln, and to the tragedy of that wall. Like a procession around a church, like if you're a Catholic and do the Stations of the Cross on Holy Week. Think of reverence, deep, deep, deep held feelings."

Much has been said, good and bad, about Kerry and his experience in Vietnam -- that it demonstrates his fitness to be president, or explains a lifelong distrust of government pronouncements about war or illustrates a calculation that has defined his career. While some, or none, of those things may be true, Vietnam also changed Kerry in a quieter, yet crucial way.

Kerry went to Vietnam for many reasons, but a key, and often overlooked motivation was curiosity. From the time he was a boy, he read military histories and World War I poetry. On the debate team at Yale and in the dorms, he loved to argue about America's use of force. Although critical of the country's role in Vietnam in a 1970 article in the New York Times, Kerry said he joined the Navy and went to Vietnam "because he wanted to study that policy firsthand." When he got there, of course, he realized it was no class trip. He discovered the difference between reading a Wilfred Owen poem and getting trapped between its bloody stanzas. Kerry went to Vietnam to learn something, but he ended up feeling something. And of all the things he felt, one of the most enduring was abandonment.

The sense that his own government had abandoned him has shaped Kerry's behavior, in politics, in friendships, and with family. Kerry is often described as a mystery, but this, perhaps, is his secret button. To a remarkable and to a sometimes self-endangering degree, Kerry doesn't leave people behind. He sticks with them, even if political advisers urge otherwise. Depending on one's outlook, one might call it Kerry's soft spot, or his most hard-core conviction.

When Kerry first ran for the Senate, Chris Gregory, a friend from his Vietnam days, tried to enlist his help to win benefits for veterans suffering from Agent Orange exposure. The government had not accepted that Agent Orange caused any illness.

"John's a skeptical person," said Gregory. "He said, 'Well, I'm not sure about this Agent Orange.' " Gregory asked him for a one-hour audience: "I knew what to do." He brought Vietnam veterans to Kerry's office -- one on crutches, one who couldn't feel his hands or feet, a widow, and the brother of a veteran who had died of cancer, leaving three young children. They talked about their mental and physical problems, and about their inability to support their families.

"At the end, Kerry looks up at me and said, 'What do I do?' He looked around, he looked at me, he looked out the door. He readjusted himself in his chair. He put his head in his hands briefly, heaved a big sigh, and said: 'Your government has left you in a place you should never be. You've been left alone.' " When Kerry got to the Senate, he worked on legislation for Agent Orange victims. Gregory wasn't surprised, judging by Kerry's reaction in their meeting.

"I knew what would happen," Gregory said. "He started to cry."

Curious About Combat

Many years on Memorial Day, Kerry walks around the Vietnam Memorial at 4 a.m. by himself. This year, a group of reporters went along on a drizzly, foggy morning. Officially, Kerry was there to dedicate a newly inscribed name, William F. Bronson Jr., a Marine from Massachusetts. Facing the black wall, he crossed himself. He hugged Bronson's white-haired mother and swallowed. "Get some peace after all these years," he told her.

After Kerry laid a wreath before Bronson's name, he stepped away from the media. The public show was over. He began to scan the names etched along the panels.

"Who are you looking for?" John Hurley, a longtime friend, asked quietly.

"Persh."

Over to the left, on Panel 39 East, Kerry found it: Richard W. Pershing.

He wiped the mist from Pershing's name. In the polished granite, Kerry could see his own reflection.

"I miss him," Kerry whispered.

By the time the war ended, five of Kerry's friends had died in Vietnam, including his childhood soul mate. Pershing was struck by a grenade while searching for a wounded comrade. When he heard the news, Kerry wrote to his friend David Thorne: "Mama wrote me and said that time would heal it. I don't think so." Pershing had died in a rice paddy, alone.

Kerry explained recently in an interview that he was running for president "with a remembrance for what they gave for the country. A huge responsibility for the rest of us to do well." His voice deepened, preemptively stern: "For anyone who thinks I'm too serious about it, I don't think you can be too serious."

Kerry laughed his hardest with Pershing, whose irreverent humor was the perfect antidote to Kerry's intensity. He was the grandson of John Joseph "Black Jack" Pershing, the World War I general. The boys had met in middle school, and remained close at Yale.

In 1965, the start of their senior year at Yale, when Vietnam was beginning to cast an increasingly dark shadow, they talked about enlisting. Pershing's attitude was straightforward: When duty calls, one answers. Kerry's father had served in the Army Air Corps in World War II and shared his friend's sense of honor. And yet, much as Kerry's heart stirred him to service, his head kept questioning it.

Kerry, by nature a debater, was the first among his friends to question the war. In June of 1966, he delivered a commencement speech casting doubt on U.S. policy: "What was an excess of isolationism has become an excess of interventionism. . . . We have not really lost the desire to serve. We question the very roots of what we are serving."

Though ambivalent, Kerry that fall entered Navy Officer Candidate School in Rhode Island. "We had the naive reasons college kids would have," said his friend Daniel Barbiero. "We thought, let's go and see what's really happening."

Kerry had read the military adventures of Teddy Roosevelt and Winston Churchill, and he fantasized about becoming a soldier-statesman, said Douglas Brinkley, author of "Tour of Duty," a Kerry biography. In high school, Kerry said in an interview, he had become interested in a career in politics: "Because that was where you made a difference -- whether you go to war, or don't go to war." His positions would be more credible, he reasoned at the time, if he spoke from experience.

After further training in California, Kerry served for a year as an ensign aboard the USS Gridley, a guided-missile frigate. In the spring of 1968, the ship pulled into Wellington, New Zealand. Over pints of ale, Kerry chatted with another officer, Wade Sanders.

"He was upbeat. He was unsure. He was ravenously curious," said Sanders. "He'd been reading the history of Vietnam. What are we doing here? What does this all mean? He talked about having seen a Swift boat. Weren't they neat? I told him I'd try to get one. He decided he wanted a closer look. He wanted to know if the war was justified."

Kerry requested a transfer to a "Swift" boat, a 50-foot gunboat that patrolled the coast of Vietnam. He was inspired by his hero, John F. Kennedy, who had served on a PT boat in World War II. Kerry carried a pillowcase full of books, from Dwight Eisenhower's "At Ease: Stories I Tell to Friends" to "Gone With the Wind."

"I joked with John it was Hemingwayesque of us, like 'Farewell to Arms,' " said Sanders. "We couldn't find ambulances to ride in the Alps, so we got small boats in Vietnam. . . . John is a journal keeper, he had a sense of his own history."

But Kerry sensed, even then, that if he engaged in -- rather than observed -- a war, he'd get trapped inside a narrative he could not control. The first time the USS Gridley approached Vietnam, he wrote about it to his fiancee, Julia Thorne:

"One can talk and talk about the meaning of war and the dangers and the horror and all the sensations that a man has when he gets near the possibility of dying. But until you actually sense them somewhat, you do not really know what you are talking about. And once you have sensed them, you tend not to want to talk about them at all."

As Kerry's airplane descended over Cam Ranh Bay in November 1968, he spotted a rainbow that ended in a splotch on the runway. He arrived just as the military changed the Swifts' mission from patrolling the coastline to churning up the Mekong Delta, baiting the enemy and destroying its encampments. Within two weeks Kerry was wounded in his arm and received the first of three Purple Hearts.

Kerry described himself in a letter as in "an uncertain state of confusion. . . . I am quite suddenly, really, in the middle of a war."

Day after day, his men roared along the jungle, through clouds of diesel and mosquitoes, blasting the Doors' "Light My Fire" to quiet their fear of snipers. Kerry, a Catholic, kept his childhood rosary beads in his pocket.

"We called it 'the days of hell,' " said Kerry's helmsman, Del Sandusky. "Going into the jaws of death." "The thing you have to remember about Kerry," said Chris Greeley, a friend, "is the government [expletive] with him -- they put him in rivers without the right boats." His men would radio for air support, and were promised backup that wouldn't arrive.

After three months, Kerry and other skippers petitioned their commanders in Saigon. "I left with the feeling that we were destined to be further cannon fodder for the task force commander -- Mad Dog Hoffman as he is known," Kerry wrote. "There is no way to explain the empty butterflies that haunted one's stomach that evening."

Kerry said in another letter that he felt homesick for the first time since he had been left alone at a boarding school when he was 11 years old. He wrote that he felt "completely, starkly removed from the familiar and the warm."

He responded to abandonment by reversing it, by turning it inside out. He became a rescuer. After a firefight with the Viet Cong, Kerry touched each of his crewmates. "He'd put his hand on my shoulder and say, 'You okay?' " said David Alston, the gunner. "There was such an adrenaline rush, sometimes he'd have to get me to stop shooting."

One day, they came across 42 sick and starving Vietnamese. Despite orders to leave the villagers, Kerry ferried them to an American base for relief. He told Brinkley, "For an afternoon, it felt good to really be helping the Vietnamese instead of destroying their villages."

Kerry even rescued a puppy, Victoria Charlotte, or VC. His crewmates bought it from villagers who were planning to cook it for dinner. "Once the bullets started flying, he'd put the dog in his flak vest against his tummy," said Sandusky. "In the middle of an ambush, she'd start shaking and she'd pee on him." Until today, the puppy stars in Kerry's war stories. Kerry's daughter, Vanessa, 27, explained: "He wanted there to be a good VC."

He had bad dreams and walked in his sleep. One night, he cried out, "I've been hit, I've been hit." Across the bunk another sleeping officer yelled, "Hang on, John, we're coming in to get you."

In his waking hours, though, it was Kerry who would shout, "Hang on!" He received a Silver Star by chasing and killing an insurgent who had aimed a grenade launcher at his men. He was awarded a Bronze Star for saving James Rassman, a Special Forces officer, who'd been blown off Kerry's boat by a mine.

Never Alone Again

Kerry joked, played guitar, took off his shoes and wiggled his toes through a hole in his blue sock during a recent interview. With kid-like confidence he demonstrated the hop-and-jump cannonball dive of Sen. John Edwards's 4-year-old son. He seemed at ease while chatting about war in the abstract. But when asked what it felt like to kill a man in combat, it was as if all of Kerry's 60 years rushed to his face at once. There was a shift from the intellectual to the emotional, and his voice withered:

"I don't talk about that stuff."

When Kerry returned from Vietnam, his face had changed. His brother, Cam, noticed it in the creases in his brow. Kerry's friends said his eyes looked sunk back in his head. His uniform was baggy. It was March 1969, and the lieutenant had come home. After he was awarded three Purple Hearts, Kerry had asked to leave Vietnam nearly six months early.

Kerry, then 27, cut a figure that was both haunting and haunted. On May 23, 1970, he married Julia, and honeymooned at the Jamaica home of his lost friend Pershing. On weekends, they visited amputees at VA hospitals, bringing them books and news. He was appalled by their neglect; it seemed like these men had been forgotten. "Boiling underneath him was a sense of betrayal," said Sanders. "A palpable anger with the way we had been treated and used."

Shortly after Kerry's return, he heard of a fellow skipper's death. His friend Donald Droz had been wounded, and while crewmates radioed for help -- "I need a medevac!" -- he bled to death. Droz left behind a widow and a 3-month-old girl. Kerry's outrage prompted the most difficult decision of his life, he said. Despite his military upbringing, Kerry decided to protest the war.

"Donnie was the catalyst," Kerry said. "I thought, 'I gotta get off my butt.' I owed Dick [Pershing] and Donnie."

Kerry understood that speaking out might make him famous, but at a time when many Americans supported the war it also might complicate his political ambitions. "I asked him, 'Do you think that's wise?' " his brother recalled. "He said, 'It's something I have to do.' "

In April 1971, Kerry led a Vietnam Veterans Against the War march in Washington. Dressed in green fatigues, he testified before the Senate Foreign Relations Committee. Accounts have focused on his recounting of war atrocities, but the real heat in his delivery came when he condemned the government for abandoning them: "We are also here to ask, and are here to ask vehemently, where are the leaders of our country? . . . We are here to ask, where are McNamara, Rostow, Bundy, Gilpatric and so many others? . . . These are commanders who have deserted their troops, and there is no more serious crime in the law of war." Kerry added: "This administration has done us the ultimate dishonor. They have attempted to disown us."

It was a long way from his graduation speech. "The difference between the Yale commencement and the Senate Foreign Relations speech is that they're both critical of U.S. policy in Vietnam, but Yale is a political science student and Washington is a visceral outcry," Cam Kerry said.

As a protester, Kerry embarked on his public life, with all its controversy and complications. But in private, with simple consistency, Kerry has stuck to a pattern. For all of Kerry's faults -- friends have called him high-maintenance, vain or long-winded -- he has been there when his friends needed him.

When George Butler, a college friend, broke his hip and femur in 1994, Kerry tracked him down the next day at a hospital in New York. Butler had been lying alone, worrying about a blood clot going to his brain. Suddenly, there was Kerry ringing his phone. He was in Tokyo, where it was 4 a.m.

Another time, Sandusky, Kerry's former helmsman, called him from Illinois and said, "I'm ready to cash it in. I can't stop the bad dreams, and I can't stop the drinking." Over the next 24 hours, Kerry talked to Sandusky -- canceling meetings, instructing aides to yank him off the Senate floor -- until his isolated friend agreed to check into a treatment center. Over the next 12 weeks, Kerry called Sandusky's doctors to make sure they hadn't forgotten his crewmate.

"John's not demonstrative, he's never comfortable with his own emotions, I mean -- he's a guy," said Gregory. "But he's extremely loyal."

Kerry has tried to pass that on to his two daughters. Vanessa recalled telling her father about a principal who had asked for assistance. "I said I don't know if I can take this on. Dad said, 'You never, ever turn your back on someone in need,' " said Vanessa. "It was a little bit of a reprimand."

Kerry's impulse is reflexive, sometimes irrational and, at times, has not served his interests. "His worst fault is being so loyal," said his wife, Teresa. "Sometimes he doesn't want to hurt people and sometimes I've told him it's better to relieve people of situations -- letting someone go you really love."

'My Thinking Place'

Tracy Droz Tragos, the daughter of the fallen skipper, heard from only one veteran while she was growing up. Kerry sent Christmas cards to her mother, a rubbing of Don's name from the Vietnam Memorial to her grandmother, and offered Tracy a Senate internship. At the end of the summer, he told the young woman who had never known her father some of Don's favorite jokes. Awkwardly, perched on his Senate couch, he hugged her while she cried.

Even so, Tragos was stunned when a reporter told her that Kerry keeps her father's picture in his private study.

"We're not important people," Tragos said, groping for words. "He knows so many fancy people, wealthy heads of state and celebrities who he could have on his desk. The fact that he has my father who was a 25-year-old man, a son of a postman from a tiny town in Missouri . . ." Her voice trailed off. "A lot has happened between now and then."

Perhaps, but Kerry doesn't let go. You can see that in his study, on the top floor of Kerry's Beacon Hill townhouse, which overlooks Boston Harbor. Kerry calls it "my thinking place. A place to keep things that are old and meaningful."

There are no plaques or political trinkets; it is a private space, for Kerry. Beside snapshots of Kerry's daughters stand photos of Droz and Pershing in uniform. There's a picture of Kerry holding VC, the puppy he had in Vietnam. Sandusky the helmsman is on the wall, too, smiling.

On a recent afternoon, Kerry spent more than an hour there, rummaging through old boxes, dipping into files. It was almost as though he had forgotten that someone else was in the room. "This is going back in time," he said, finding a map of the Mekong Delta. he pointed to a turn in the blue, jagged river: "This is where we got ambushed on Christmas."

Kerry dug out the legal pad where he'd scribbled notes for his 1971 speech to the Foreign Relations Committee. It began as a letter: "Dear American, supporter of the boys in Viet Nam . . . I want you to understand the anger and sense of betrayal . . . "

He opened his diary and read about his last day in Vietnam: "When I left there was no rainbow arcing into the runway. And there was no rain. But especially I remembered the rainbow because I had been stupid enough to wonder if there was a 'pot of gold' waiting for me in Vietnam. There was romance then: People only died in accidents, in hospitals, in war stories . . . but there was no romance the day that I left. . . . I had learned about stupidity, and absurdity, and war crap, and dead men -- " He interrupted himself. "You can see how angry I was."

An aide walked into Kerry's study for the third time. "Your 4:30 phone call is waiting." It was 4:50 pm.

He walked down the stairs, toward the living room. In his striped shirt and tie Kerry looked like any other politician. Then he reached into his suit pocket. In the light of the stairwell, a piece of metal glinted in his hand. It was his dog tag, his identity, stripped to its essentials: "Kerry john f. Service # Usn Rom cath. Blood type O."

He carries the chain in his pocket, always: "This brought me home safe." In Vietnam, he had taped the dog tags together so they wouldn't rattle during secret missions. There's still a piece of tape on it, but the second dog tag is missing.

"Alex, my daughter, has it," he said.

Kerry had given it to Alexandra when she was going through a hard time. He wanted her to know that her father was with her always. That she would never be alone.

Staff writer Dale Russakoff contributed to this report.

Kerry, far right, in Vietnam. "One can talk and talk about the meaning of war and the dangers and the horror . . . ," he wrote then. "But until you actually sense them somewhat, you do not really know what you are talking about."John Kerry testifies before the Senate Foreign Relations Committee, chaired by William Fulbright, in April 1971.Kerry received a Silver Star and a Bronze Star for his service in Vietnam. He also was awarded three Purple Hearts.On the campaign trail in Iowa this January, Kerry was reunited with Jim Rassman, whom he saved in the Mekong Delta.At the Vietnam Memorial, Kerry hugs Barbara Bronson, the mother of a veteran whose name was added to the Wall this Memorial Day.