Honor: so intangible, yet so powerful. The glue, some soldiers say, of any fighting force; the raison d'etre of many a soldier.

The Honor Code. The Honor Guard. "Honor-bound to defend freedom." That's from a placard at the U.S. military prison at Guantanamo Bay. And that catchphrase from the Vietnam War, about an oh-so-elusive "peace with honor."

If it's military, it's about honor. Without it, a soldier is a rogue. A scoundrel. Perhaps a war criminal? A politically opportunistic veteran? A John E. O'Neill, he of the Swift Boat Veterans for Truth? Or a Sen. John Kerry, the very decorated but embattled soldier who wants to be commander in chief?

So valued is this sense of honor that the allegation of dishonor hits like heavy ordnance. And for weeks, the Swift boat veterans have been firing away -- just as they feel they were fired on, by Kerry, some 33 years ago when the decorated young vet likened the U.S. military in Vietnam to war criminals.

For decades, some veterans have massaged their anger, have polished their grudge. Then they exploded on the scene with a vengeance, propelled by the presidential campaign, to do to Kerry what they believe he did to them: attach dishonor to his name. Why now after all these years? Some say it's politics. Some say it's the lasting sting of being called a war criminal.

Whatever it is now, it started as a battle over honor.

"In the old days, people fought duels over honor," says Mackubin "Mac" Owens, a retired Marine Corps colonel and a professor at the Naval War College. He's not one of the angry Swifties, as they are called, though he agrees that Kerry dishonored the troops by pointing up war crimes during his 1971 congressional testimony.

"In certain respects, what you have here is a latter-day example of a duel," Owens says. "In the old days, if I had been there and John Kerry had walked out of the Senate in 1971, I would have taken a glove and slapped him in his face and told him to choose his arms."

As if in combat, obscure veterans are popping up from the foxholes of their lives to support one side or the other.

Perhaps one of the best-known Vietnam veterans, Sen. John McCain (R-Ariz.), is serving as a kind of arbiter of honor, pronouncing the Navy combat service of Kerry and the noncombat National Guard service of President Bush equally honorable.

This is about more than service, though. It's about the cultural wars that have rumbled along the country's ideological fault lines for decades since Vietnam.

It would be simple to paint the debate with stereotypes: between those who loved the smell of napalm in the morning and those who made love, not war. Really this is a debate about the morality of the Vietnam War itself -- between those who supported it and those who didn't; those who fought in it with no complaints and those who fought but then protested.

It parallels the fissures in society that have calcified over the past 30 years.

"Opposition to the war was conjoining with the civil rights movement, conjoining with the women's rights movement," says Roger Wilkins, a George Mason University historian.

"There was an enormous amount of social upheaval. A whole bunch of things were challenged at the same time and it shook the culture to its core, and in fact created the political and cultural rift that we see in the current election" campaign.

Which is why Wilkins sees the Swift Boat Veterans crusade as less an issue of honor and more one of partisan politics.

"I suspect there are guys in the country, maybe even a few among these Swift boat guys, who are doing it about honor," he says. "But I think basically the Swift guys are in there because they like W."

But the Swifties say they feel their sense of dishonor deeply, abidingly. And it predates the campaign, though they had not acted on it.

Their feelings are in keeping with the Homeric idea of honor that still courses through the military culture, says Rosemary Mariner, a retired Navy aviator and now a military historian. Honor resides in the recognition of one's peers, the approval of one's superiors, as in the example of Achilles, the mythic Greek warrior of Homer's "Iliad."

"So the whole business of Achilles' wrath is because his commander in chief, Agamemnon, has dissed him."

Mariner is a professor with the Center for the Study of War and Society at the University of Tennessee. Earlier this year, for her class on Vietnam, she viewed a tape of a 1971 Vietnam War debate between Kerry and O'Neill.

What seemed so striking to Mariner was O'Neill's anger. An anger that reminded her, she says, of the "wrath of Achilles."

Oh, yes, no doubt about it, says O'Neill.

"We've been very angry about this speech for a long time."

When he heard Kerry liken U.S. troops in Vietnam to the marauding campaigns of Genghis Khan, "That's a moment I've never forgotten in my life." As a touchstone moment in his life, he says, it ranks with the Kennedy assassination and the Challenger space shuttle disaster.

Never mind that Kerry has said that perhaps he succumbed to youthful overstatement. O'Neill still feels the burn, still feels that hard contempt.

He is the author of "Unfit for Command," an anti-Kerry book released this month.

What is this thing, this honor? It is, he says, "the link that makes it all work." The adhesive of military life. You've got these young people, earning little money, in a far-off land, risking their lives.

"Why are they there? Well they're there for the dignity of serving the country, and they're doing the right thing," he says.

That's the "honor of service," he says. It makes it possible for people to accept the sacrifices involved.

But the moment of dishonor occurred in 1971. So why now?

"We're talking about commander in chief of the United States," he says of Kerry's presidential ambition.

The Swifties want him stopped.

Separate it from the presidential campaign, though, and the dispute over honor in the military is nothing new.

"Catfights over military service are as old as the republic," says G. Kurt Piehler, director of the Center for the Study of War and Society.

Take Longstreet and Lee, for instance. Gen. James Longstreet lost his honor, in the eyes of fellow Confederates, for criticizing the war strategy of Confederate commander Robert E. Lee during the Civil War.

"Virtually every war will create these controversies," says Piehler.

Already, the first drafts of history on the war in Iraq are laying the groundwork for future debates. Think Abu Ghraib. Think WMD or lack thereof.

The Iraq conflict -- another war full of controversy. The similarities haven't escaped Diane Acosta. She's a state prosecutor from Arizona who was visiting the Vietnam Veterans Memorial the other day when she said of Vietnam, "I think people always will debate it."

They will continue to question the morality of the war, whether there was honor in it.

They will ask: "Should we even be there? And once we're there, what do we do?"

Acosta's change of tense seems to conflate Iraq and Vietnam. The questions, she says, are "for both."

She and her husband, Don Acosta, retired from an arms manufacturer, aren't too taken with the whole debate about honor and who's got more of it. Don Acosta, 56, sees it simply.

"I have friends on that wall," he says solemnly. He's remembering one friend in particular, a Michigan kid named Mike Elmy.

"I'm flashing back right now to that afternoon," Acosta says of his youth in Pontiac. "The neighborhood was on the porch when the Army officials pulled up to tell them they'd found Mike's remains."

To Acosta, who did not fight in the war, the honor of service is in just being there. And Kerry was there.

"He could be on this wall, too. Very easily," Acosta says. "Did he cut and run? I just don't believe that. . . . Not that I'm a big Kerry man, 'cause I'm not."

He's a Bush man. Was in 2000, will be again. Still, he jabs a finger toward that granite wall and says emphatically of Kerry, "I think he stepped up [to the plate] with these folks."

The Vietnam Veterans Memorial: Intangible honor, set in stone.Vietnam veterans opposed to John Kerry demonstrate outside the Fleet Center in Boston during last month's Democratic National Convention.