"I was a formed, mature individual," McCain says. "I was married. I was serious about my military career."

But prison and torture must change a man. The John McCain who landed with his fellow POWs at Clark Air Force Base in the Philippines in 1973, liberated after five-and-a-half years of confinement, was a different person.

The jet jockey had learned humility. The rebel had felt the power of a higher cause. The loner had come to understand dependence. The admiral's golden boy had been face-to-face with his own fallibility, and emerged a more forgiving soul. It was, McCain says, "a refining experience."

Before Vietnam, " he was always an individualist," says Mark Salter, McCain's biographer and speechwriter. In the crucible of the POW camps, "he learned it wasn't enough."

McCain is 63 now, and his father and grandfather are long dead. But his story must begin with them, for it is hard to overestimate the impact that their legacy had on his life. Both were decorated combat veterans, and four-star admirals. Both were hard-drinking men's men, adept at profanity, dedicated to the United States and its Navy. Both spent huge chunks of time at war or at sea, away from their wives and children.

With such a pedigree, it was preordained that young John, after the rootless childhood of a Navy brat, would follow them into the US Naval Academy and the officer corps. He did so, but only in what he now recalls as "a very rebellious period in my life."

"He had a little bit of internal conflict. His legacy weighed heavy on him," says Frank Gamboa, a Naval Academy roommate. "I was there because I wanted to be there. He was there because it was the family business. He felt he didn't have a choice. He was very proud of his father, and of the Navy, and felt comfortable, but at the same time his lack of freedom of choosing his own way bothered him."

Because of his background, McCain also recognized that the Naval Academy was not the Navy, that the ability to endure the upperclassmen's hazing or shine one's shoes had little to do with the grit that was needed to land a jet on an aircraft carrier, or play hide-and-seek with an enemy destroyer.

"Most of us were not from a military background and had busted our asses to get to Annapolis. But because he was a Navy junior and because his father and grandfather each had a salty character and acquired their own substantial degree of demerits -- it was a family characteristic -- it gave him a psychological safety net that none of the rest of us had," says Gamboa. "He developed a reputation for pushing the limits."

McCain drank to excess. He led expeditions of randy midshipmen "over the wall" without leave. He had a storied love affair with a Brazilian fashion model. "I was an arrogant, undisciplined, insolent midshipman who felt it necessary to prove my mettle by challenging...authority," McCain recalls in his memoir, "Faith of My Fathers. " "In short, I acted like a jerk."

McCain's gang of carousing classmates was known as the Bad Bunch. He collected demerits by the dozens, and just narrowly avoided expulsion. After graduating in 1958 near the bottom of his class he maintained his wicked ways while training and serving as a pilot -- at one point dating an exotic dancer known as Marie, the Flame of Florida. The officers' wives watched wide-eyed when she cleaned her nails with a switchblade.

It was a more mature John McCain who took off from the aircraft carrier USS Oriskany to attack Hanoi in October 1967. He had emerged without serious injury from three potentially-fatal flying accidents, worked his way up through the ranks, and been married in 1965. The Navy was now his life. "The limits of my ambition were to be a squadron commander," he recalls.

In July of 1967 McCain had watched friends and shipmates die before his eyes when a fire and explosions wracked his ship, the USS Forrestal, while on station in the Tonkin Gulf. He himself was wounded by shrapnel from exploding bombs, and burned when his jet was destroyed by the malfunctioning rocket that set off the conflagration.

"John, being the son and grandson of admirals, had a keen sense of what it meant to be a naval officer. But on the Forrestal he saw everything he had heard about -- the immense tragedy, the personal sacrifice," says Orson Swindle, a fellow POW. "He not only saw it, but was damn near one of the dead. The vast majority of men would have taken that as a ticket to avoid further sacrifice. But he goes and gets on another ship and goes back to war."

On Oct. 26, 1967, while on his 23d mission over North Vietnam, McCain's A-4 fighter-bomber was hit by a surface-to-air missile. As he ejected from the airplane, he broke both arms and a knee. The Vietnamese who rescued him from a Hanoi lake broke his shoulder, beat, and stabbed him. He was interrogated by guards who beat upon his broken bones. Suffering from fever and dysentery, he was ultimately delivered to a POW compound known as "the Plantation."

"When I got him he was absolutely on the verge of death. His right arm was broken. His left arm had been pulled out of the socket. His right knee had been fractured and cut on. He had been bayoneted. He weighed somewhere between 95 and 105 pounds. He was filthy rotten stinking: You could smell him 15 or 20 feet away. They had battered and tortured him," says George "Bud" Day, an Air Force major who was awarded the Congressional Medal of Honor for his heroic resistance to their Vietnamese captors.

"I had no doubt they had dumped him on me so they could say he died in the care of an American," says Day. "It was fascinating to watch him fight back. His body was telling him, we're going to die. His brain was saying, the hell we are."

John McCain is no saint. His first marriage failed when, after returning from Vietnam, he was unfaithful to his long-suffering wife. There were reports at the time, which he denied, of affairs with subordinate female personnel. He must work to control that now-famous temper. Like many elected officials, he has crossed the line at which constituent service evolves into favors for special interests -- most notably in the 1980s for Charles Keating, the convicted savings and loan kingpin.

Yet the McCain that emerged from Vietnam has a certain depth and strength of spirit that marks him as more than the average fighter jock, or politician, says writer Robert Timberg.

"All of us have, at various times, a need to test ourselves or be tested. And we wonder if that moment ever comes, how we will respond. Most of us never really face that moment. But he faced it. He found out he could stand up to damn near anything. Because he had," says Timberg, a Vietnam veteran and the author of "John McCain: An American Odyssey. "

Honor demanded that, unless a man was seriously ill, the POWs could only go home in the order by which they were captured. McCain, though lingering near death, turned down the opportunity for early release because it would have given the Vietnamese a propaganda coup: his father was then the commander-in-chief of naval forces in the Pacific.

"He recognized immediately that he was, as son of a famous admiral, a major liability to the United States. They tried to get him to go home, and he was damn near dead, but John McCain said, `No, I'm not doing it,"' says Swindle.

McCain ultimately drew confidence from having passed that test, says Timberg. Such self-knowledge reinforced his natural feistiness, and helps explain McCain's willingness to tread the less-worn paths in politics.

Salter believes that the POW experience taught McCain the limits of a lone-wolf existence. Bud Day and the other POWs saved McCain's life, and kept him sane. By submerging his ego in the organized resistance of the POWs, says Salter, McCain learned the virtues of sacrifice, and the power of being part of something greater than self-interest.

"He learned that it wasn't enough, that no human being could handle it alone. That he had to become part of a greater whole. And he learned the satisfaction of being part of something that encompassed him, yet liberated him," says Salter.

McCain emerged from Vietnam with a stronger sense of duty and public service than before. "It wasn't until I was deprived of her company that I fell in love with America," he says.

The POWs were freed in 1973. McCain and the others were welcomed home like heroes. His family treated him with deference, not wanting to probe or pester him as he made the adjustment to normal life.

McCain's brother Joe waited a while, then went to see him in California. John McCain picked his brother up at the airport in a convertible, and seemed his old charming self at the base officer's club, or when driving around town.

"But every now and then he fell really quiet," Joe McCain recalls. "John had always been a guy constantly in motion: social motion, verbal motion, mental motion. Partying. Arguing. Fussing. Having fun. Being a pilot. Now he seemed to be focusing on who he was, as opposed to just living in the moment.

"I got the feeling that what had changed in him was that the experience had taken what was inside of him and condensed it. Tempered it, like steel," says Joe McCain. "He was a lot more reflective. He came out looking more forward, and more backward. It all made him think about that inner gyroscope, that compass."

Central to these changes were the lessons McCain learned from the times he failed: when the pain and fear caused him to act less nobly, and submit to his jailers. To this day, McCain is haunted by a confession he signed in Vietnam, under torture, confessing to being a "black criminal" and an "air pirate.''

"He was obsessed and tortured by guilt. We all were. To this day I get angry with myself,'' says Swindle. "But we did the best we could. And he realizes, over time, that we all fall short of what we aspire to be. And that is where forgiveness comes in."

On several notable occasions since he returned from the war -- when battling POW-MIA profiteers, reaching out to old foes from the antiwar movement, or giving President Bill Clinton the political cover to normalize relations with Vietnam -- McCain displayed true forgiveness.

When Clinton-hating veterans challenged the President's right to visit the Vietnam Veteran's Memorial in Washington, McCain offered to escort the commander in chief. And it was McCain who defended and befriended antiwar leader David Ifshin in the years before his death from cancer in 1997, though Ifshin had been one of those students who traveled to Hanoi and made propaganda broadcasts for the North Vietnamese, which had been piped into McCain's cell.

McCain's ability "to move on " is perhaps the most impressive legacy of his time in POW hell.

"The closeness of the relationship that we developed in prison is hard to adequately describe," he explains. "And the senior officers, especially, recognized that many of us were weak, and sometimes didn't do too well under the pressure of our interrogators, as perhaps we would have liked to. They displayed compassion by encouraging us, even if we had failed, to go back again and do better next time."

It is a lesson he never forgot.

"Oh yeah. Oh yeah," McCain says, sitting in a straight-backed chair, his elbows on his knees, staring at the floor as he answers the question. "Recognition of my own failures had the obvious result of making me a lot more tolerant of the failings of others.

"There are individual Vietnamese who, if I saw them again, I am sure I would attempt to inflict some physical punishment," he says. "But the South Vietnamese were our allies and friends, and they are now part of overall Vietnam.

"And my job...was to help the healing and reconciliation process, so we could give help to those Vietnam veterans who had not come all the way home, to continue that journey," McCain says.