In 1968, Nelson DeMille fought in Vietnam as a lieutenant with the U.S. Army's First Cavalry Division. Thirty-nine years later, he went back--this time on assignment for a travel magazine. The author wasn't planning to write another book about the war, but, inevitably, he did.

"While I was there it occurred to me that all this traveling in a Third World country must have a better purpose," says DeMille. "So I said 'maybe I should revisit Vietnam one more time while I can still remember it'."

"Up Country" (Warner, $26.95), due in bookstores Jan. 29, resurrects Paul Brenner, the wise-cracking military investigator played by John Travolta in the movie version of DeMille's "The General's Daughter" (1992). In "Up Country," Brenner is sent to Vietnam on a top-secret investigation into the 30-year-old war murder. Like DeMille's previous books, the plot writhes with twists, turns and people who aren't what they seem. There are car chases, shoot-outs, and a smart, sexy love interest in the form of American expatriate Susan Weber. But unlike some of DeMille's earlier works, "Up Country" is distinctly political and didactic. Brenner is portrayed as a Vietnam veteran who, like DeMille, served in the First Cavalry. He is outspokenly critical of the current Vietnamese government-both its policies and its treatment of the South Vietnamese soldiers who were allied with the United States. En route to solving the murder mystery, Brenner revisits his old battlefields, where he takes the opportunity to enlighten the younger Susan about what it was really like on the ground for the foot soldiers of America's controversial war.

Shortly before beginning a national promotional tour, DeMille spoke to NEWSWEEK's Arlene Getz about why he wrote "Up Country"-and how his writing has been affected by the September 11 attacks on New York and Washington. Excerpts:

NEWSWEEK: Does the political style and tone of "Up Country" represent a new direction in your writing?

Nelson DeMille: No, I don't think I would do it again. I try to avoid being polemic[al] or even coming down on one side or the other. I can usually do that in books that I'm not involved with, but this did bring back a lot of memories for me. The eye-opener for me was going to Vietnam [in 1997] and realizing that they did win-and we didn't.

Your character, Paul Brenner, finds his return to Vietnam very emotional and painful. Is that how it was for you?

It was in a lot of ways. But [I went] with two guys who were there in that same year [as me], guys that I've known since childhood, and they were both combat veterans, too. I think that helped in itself.

But you did want the book to be more than a thriller? To educate readers under 35 about the politics and the conflict of that era?

I tend not to be political in my books. There's some politics in all of them, but I'm not a political writer, I'm not Tom Clancy. I consider myself even-handed, but I think it was an emotional issue for me. I wanted to write something more than a thriller, and yes, it really was the younger generation that I was looking at. My two children, now 21 and 23, have asked me a lot of questions about Vietnam. I had them in mind. I tried to call it as I saw it.

Do you expect the book to rekindle the debate about the war-especially since America is now involved in another war in Afghanistan?

I think Vietnam is almost a dead issue because of the situation since September 11. But I think as a thinking people who want to know how we got where we got-the war still resonates. You can't have a discussion about the gulf war or the current war without talking about Vietnam.

Your lead male characters are invariably smart, irreverent, witty, sexy and mature. Is that you as you are, or you as you'd like to be?

Yeah, I think I'm kind of like that [laughs]. Still holding it together at 58. When I can remember to be witty, I am witty. Which brings us to another subject. A lot of women respond to my books. These books are kind of muscular in some ways, but most of my fan mail comes from women. That's probably because women tend to write, men do not.

Yes, you are one of those relatively rare writers who appeals both to men and women. What's the attraction?

It has to be the male characters. That's the only thing I can think of. It's not so much that I create strong female characters. The women that come to my book signings, the women who write me, are not responding to that. For the most part they're responding to the character of either Paul Brenner or John Corey [from 1997's "Plum Island" and 2000's "The Lion's Game"] or one of the male characters that I've created. There's a lot of women out there who really don't like sensitive men. They like guys who can take care of business, but not Neanderthals either. This seems to be the common thread that I get. Every fan letter I get says I'm in love with John Corey, I'm in love with Paul Brenner.

What's your agenda when you write?

You have to keep in mind always that it's got to be a page-turner, that it's got to be commercial popular fiction on one level, or nobody's going to read it. I guess what I try to do is slip some messages and observations in. That's what I try to do with most of my books. But it's like medicine sometimes-you have to put a lot of sugar on it. It's easier to write a polemic; it's easier to write a piece of serious fiction, but if you're looking for readership its got to work on many levels. You have to entertain and teach at the same time.

Your last book, "The Lion's Game," was about an Arab terrorist who slips into the U.S. after killing all the passengers on his plane-and then shows how easy it is for foreigners to rent private aircraft and move around the country undetected. How did you feel about that on September 11?

Some editors, even some fans, said at the time, "you're way over the top about the Arab terrorists." It now turns out that, if anything, I was understated. Some of the negative fan mail and the reviews said I'd demonized Middle-Easterners. [But] I tried to be even-handed with this guy, Assad Khalil. Nasty as he was, you could see where he was coming from.

How did you come up with some of the terrorist plot lines in that book?

I'd spoken to a lot of people from the antiterrorist task force in New York. They knew that Arabs were training in the United States to fly small planes. One of the [task force] scenarios was that because general aviation is so unguarded, a small light plane full of explosives would crash into the World Trade Center. They said the World Trade Center was the target because they missed it in '93. They said this years before [September 11]. I didn't get it into the book. I'm kind of sorry about that-not to exploit the situation, but as a kind of wake-up call, an alert.

Your books invariably provide an insider's view of crime-fighting agencies. Is it accurate?

I try to make it as factual as I can. I don't normally take literary license unless I'm really forced to, and in this particular case ["The Lion's Game"] I really did spend a lot of time with Joint Terrorist Task Force guys ... They realize you're not a reporter, that you're going to write a work of fiction, so they tend to open up a little bit more than they would to a journalist. You have to win their confidence, and not betray it.

Another of your books, "Gold Coast," is also being made into a movie.

Yes, it's with Al Pacino, and I believe shooting is beginning in Montreal in March. Then they're moving it to Long Island and New York. Harold Becker, who did "Sea of Love" (1989) and a whole bunch of other things, is directing it.

Will "Up Country" also hit the big screen?

It's just been bought by Paramount, and they want to make it as a sequel to "The General's Daughter."

With John Travolta star as Paul Brenner again?

Yes, Travolta apparently is interested. ["The General's Daughter"] was a successful movie for him-maybe not critically, but I think he did a good job-[and] it was successful financially for everybody. Paramount [was] going to make their own original sequel based on the screenplay, but I let them know I was writing a sequel anyway, so they waited for it.

What are you working on now?

Actually, nothing. Because of September 11, I'm just trying to figure out what the next book should be. And I just can't. I spoke to at least 10 writers over the Christmas holidays, and we all came up with the same conclusion-that we don't know what to do right now.

So the attacks on September 11 have caused writer's block?

Not so much writer's block. But when you have times of national crisis, like World War II, a lot of writers retreated into historical novels, if they were able to write them. A simpler time, a more heroic time that was supposed to be an inspiration for the present. Some writers retreated into the mystery because it's timeless, and some writers go for the love story. [But] for action-adventure, commercial fiction writers, you don't know what to do. You don't know whether to ignore what's happening, or mention it in passing or make it central to the book.

As a novelist with a two-year lead time, do you want to deal with it now [when] it might be irrelevant by the time that you do it? Whatever you start today should still be resonating when the paperback comes out four years later.