When Modern Library brought out the 20th edition of David Halberstam's Vietnam War classic, "The Best and the Brightest," in 2001, the publishing house made a surprising choice to write the foreword: hawkish Republican presidential contender John McCain.

It's not that the Arizona senator wasn't an inspired selection. One can only imagine how a man who spent 5 1/2 years suffering in Vietnamese prisons felt on learning that many of the justifications for the war that mangled his body turned out to be hubris-fueled lies -- particularly because it was his own father, Adm. John Sidney McCain Jr., who, as commander in chief of the U.S. Pacific Command, led the military effort during most of his time behind bars.

No, the surprise is that McCain would agree to write about a subject on which he's been remarkably silent and unreflective over the years: how and when the U.S. should decide to go to war.

Perhaps not surprisingly, McCain doesn't think that he's been unthoughtful on the subject; in fact, he thinks he's wrestled it to the ground. "Soon after I came home," McCain wrote in the foreword to the Halberstam book, "the Navy allowed me to attend the National War College for a year. There I arranged sort of a private tutorial on the war, choosing all the texts myself, in the hope that I might better understand how we came to be involved in the war and why, after paying such a terrible cost, we lost."

And there does appear to have been an evolution in his thinking around that time. Before entering the National War College that year, McCain had been an enthusiastic believer in the "domino theory" -- the notion that should Vietnam fall to communists, the victors would then export their murderous ideology to the rest of Southeast Asia, one country at a time.

"Some people's favorite game is to refute the 'domino theory,' " McCain wrote in an essay for U.S. News & World Report before starting at the War College. "But the North Vietnamese themselves never tried to refute it. They believe it."

Today, like most of the world, McCain no longer believes in the domino theory. And there's every reason to suspect that he changed his mind while studying at the War College, during which time he says he gorged on French colonial history, Graham Greene novels and the Pentagon Papers. (The latter despite volunteering to testify in court against Daniel Ellsberg for leaking them.)

"By the time my nine months of study at the War College ended, I had satisfied my curiosity about how America had entered and lost the Vietnam War," he wrote in his 2002 political memoir, "Worth the Fighting For."

"The experience did not cause me to conclude that the war was wrong," he wrote, "but it did help me understand how wrongly it had been fought and led."

How did his views change once confronted with all the damning new evidence about justifications for war? He does not say.

So it's no wonder that those of us who have written about McCain's life have been desperate to lay our hands on that April 1974 National War College thesis. In the quest to understand how his Vietnam experience has affected his views on the unpopular war in Iraq, it's been like a hunt for the Rosetta Stone. Surely it would provide glimpses into his thinking, and evidence of the kind of doubt that helped make him an outspoken skeptic in later years of U.S. deployments to Lebanon, Haiti and Bosnia. And maybe it would contain a hint of why he wants to double down on an even less-popular war.

No such luck.

I recently obtained a copy of McCain's essay through a Freedom of Information Act request. And, quite unlike the senator's own descriptions of his nine-month course ("to study why and how my country had fought in Vietnam"), the paper isn't actually about any of that. It's instead a relatively technical assessment of how the military's post-Korean War changes to the Code of Conduct for POWs played out on the ground in Vietnam.

What does the wide gap between stated subject and actual essay tell us about John McCain?

For one, that he had a soldier's sense of contributing where he could be useful -- that is, relating the experiences of his fellow prisoners -- while leaving the big-picture agonizing to others. (When asked by National Public Radio interviewer Terry Gross in 2000 whether he would have gone to Vietnam knowing everything he now knows, McCain answered, "I think that I would have had significant questions, but I believe that as a career military officer, I still would have gone.")

So are there any modern geopolitical insights to be gleaned from McCain's 33-year-old essay on how the POW Code of Conduct should be modified slightly? A few, yes.

Those wanting to understand why the senator continues his lonely GOP opposition to waterboarding and other high-stress interrogation methods need look no further than the paper's withering contempt for the "flagrant violations by most communist governments of the Geneva Conventions." Interesting (and equally understandable) is his disgust at visiting antiwar delegations in Hanoi, and his regret that the POWs became too much of a cause celebre back home, forcing the U.S. government to let them become bargaining chips.

But on the question of whether the war should have been fought, the only hint comes in McCain's scorn for the way it was waged. "Unconditional surrender," McCain laments, "has not been our stated objective since 1945." President Johnson, he complains, did not fight "to win."

If there is any truly contemporary echo in his War College paper, it's that U.S. troops cannot fight to the best of their abilities if they do not personally support the policies they're enforcing and if they do not have the support of the American people.

"The biggest factor in a man's ability to perform creditably as a prisoner of war is a strong belief in the correctness of his [nation's] foreign policy," he wrote. "It is [incumbent] upon the armed forces before sending its members to fight, and possibly die, to inform them as to the nature of the foreign policy and goals of the United States of America. ...

"A program of this nature could be construed as 'brainwashing' or 'thought control' and could be a target for a great deal of criticism. But if a program of this nature was well formulated and professionally executed it would be of inestimable value."

So McCain didn't necessarily attend the National War College to assess the wisdom of Vietnam. But he did reinforce a belief system that he's carried to the present day: If you must fight, fight to win, and keep explaining to the American people all along why the sacrifice is necessary. Come January, we'll begin to find out whether McCain's message is resonating.

Matt Welch, a former assistant editorial page editor at The Times, is an editor at Reason magazine and author of "McCain: The Myth of a Maverick."