Francis O'Brien is frequently asked how one becomes a movie producer. He should know, because he is the executive producer of "Gallipoli," a saga of Australian lads en route to World War I, which has excited critics and is selling out simulataneously in New York and Sydney.

O'Brien never knows quite how to answer.

"What am I going to tell them -- go impeach a president? Study Chinese in college? Then you're sure to wind up in Australia, sleeping on location with a film crew? Actually, when I look at what's happened to me, it's more like a course in how not to get into the movies."

He is 38, his trousers have a crease, and he wears an expensive rectangular wristwatch. But after growing up in Sandusky, Ohio, and college at Miami of Ohio, he came to Georgetown University to further his interest in Chinese studies, and after that wound up teaching social studies at Anacostia High School. And then went to New York, and John Lindsay. And then back to Washington again, where he became the administrative asistant to Rep. Peter Rodino (D-N.J.). Rodino was chairman of the House Judiciary Committee. The year was 1973.

"No -- I didn't know," O'Brien said. "I just thought I was going to work for a congressman from New Jersey."

Within a year, O'Brien had become a key figure in the impeachment hearings of President Richard M. Nixon. Reporters who covered that devisive, embattled time remember him as a brilliant young strategist and administrator, a man quickly scooped up by Walter Mondale for his own campaign in 1976. O'Brien remembers those days, too. But he is in the movie business now. How he got where he is seems of less interest to him than where he has gotten to; which, as it happens, is Australia.

"After Mondale I'd gone to Paramount as director of marketing, but by 1979 I was on my own again -- just looking for something I could do. I'd gotten to know Robert Stigwood from working on 'Grease' and 'Saturday Night Fever,' and Stigwood and Rupert Murdoch sent me off to Australia," he recalled. " 'Go see if there's a film industry there,' they said. So I went. You know, it's 30 hours away by plane. I just arrived quietly and started going to the movies. In two months I had seen every movie in Australia and met 12 directors whom I believe are world-class. My report was, yes, there is a film industry there, and I have found a film to make." The film was "Gallipoli," to be directed by Peter Weir from his own story.

Stigwood and Murdock said, "Here's $3 million -- go make it." They formed a new corporation, Associated R&R Films, and named O'Brien president.

Weir was already an established director down under, and two of his films -- "The Last Wave" and "Picnic At Hanging Rock" -- have attracted attention in the United States. Other directors, among them Bruce Beresford ("Breaker Morant," "The Getting of Wisdom"), Fred Schepisi ("The Chant of Jimmie Blacksmith") and Gillian Armstrong ("My Brilliant Career") were also being held up as evidence of an emerging film industry on the far southern continent.

But Australia, O'Brien found, was still very much a frontier of moviemaking. For one thing, no Australian film had ever cost more than $1 million -- for the simple reason that in a nation of 14 million people, a return on a larger investment seemed unlikely. "Breaker Morant" cost only $800,000, and "Gallipoli" is by far the most ambitious financial commitment in that nation's movie history.

"The appeal of Australia is not the location, although films can certainly be made cheaply there," O'Brien said. "The appeal, frankly, is the talent, especially in directors."

If "Gallipoli" was a word that at first meant little to O'Brien, he quickly found that the beachhead assaults on that Turkish peninsula on April 25, 1915, meant everything to Australians. "Peter had spent two days touring the battlefield, and decided it was the film he wanted to make," O'Brien said.

Sixty-five years afterwards, O'Brien found himself in the Australian desert, sleeping under the stars with a director and film crew in order to tell that story.

"A producer can define his job however he likes," O'Brien said. "Remember, I went down there knowing that every American distributor had already passed on our project in script form. They said, 'Oh, no period movies. No movies that aren't upbeat.' And, God knows, no foreign movies. So naturally I wanted to stay close.

"Actually, we all lived the same way -- the director, the actors and the lowliest grips. Extremely primitive surrounding. We ate beef and beans off tin plates. But the Australian film crews coped, because they'd never known any other way."

At close range, O'Brien found, the natural tensions between director and producer -- mostly over the budget -- were possible to resolve together, as when Weir wanted to break the texture of sweaty male camaraderie with a formal dance scene showing officers waltzing happily with green-clad nurses.

"If I'd been $15,000 miles away," O'Brien said, "I'm sure that idea would have seemed just director's ego. But being there, I knew he was right. The film needed a lyrical break before moving on to the horrors of war. So we budgeted another $100,000."

Weir had also devised an unusual underwater scene, in which the soliders frolic in the surf during an aerial bombardment at Gallipoli. O'Brien didn't want to spend the money on it.

"I finally said, 'All right -- but let's hold off. We'll go ahead without that scene, and when we put together the first cut, see if you still think it's essential. If you still think it is, we'll shoot it then.' He went along with me and, as it happened, he was right. The underwater scene is essential to the core of the film, and we shot it later and put it in."

O'Brien's job was to bring in the finished film, and after months in the editing room "Gallipoli" emerged with some finishing touches of his own. It was he who chose the dirge-like Adagio in G Minor by Albinoni that provides ambiguity for otherwise fresh-faced scenes, and he who fought also for the synthesized music of the contemporary French composer Jean Michel Jarre.

"I suppose music is just my own favorite art form. We hadn't budgeted for an original score, so the selection fell to me. All through the project I had been thinking of the Albinoni. Then, as we were watching the dailies, the Jarre just came to mind. Somebody said, 'You can't use music that wasn't even written in 1915.' 'Well,' I said, 'the Albinoni isn't exactly music of the period, either.' "

"Gallipoli" was finished, but it still had no distributor. O'Brien started showing it around Los Angeles.

"Three companies liked it," he recalled. "One said, 'great -- but would you go back and put a little more romance in? ' Another asked if we would mind changing the ending. 'No problem,' I told them. 'You give us $3 million and we'll make a film like that. But this one is already made.' "

It was Paramount -- O'Brien's former employer, where he had the influence of his own reputation -- which took the film as presented.

In its initial openings in New York, Los Angeles, Toronto and Vancouver, "Gallipoli" has been playing to filled houses. Whether a story of Australians in World War I will prove compelling for Americans remains to be seen, but the market down under was a better gamble. "The lines in Sydney are just phenomenal," O'Brien said. "You still can't get in to see it after three weeks. We had counted on that, and it's happened."

O'Brien's Washington friends, some of whom are well-known reporters, insist that Francis O'Brien's is a case of high competency in an uncracked container. They are telling him he's got it made now, and that, what's more, they always knew he could do it.

He shakes his head a little ruefully at such congratulations.

"It makes me look back at impeachment," he said. "Now we look good. But in 1974 everybody was yelling at us, and calling us names. Today, I can say that yes, 'Gallipoli' is going very well, and we look good. Two weeks ago I wasn't so sure. What it all comes down to is doing what you want to do, whatever it is. We're going to make some more movies down there. R&R is probably going to do a kidnapping story by Bruce Beresford. And I've been talking to Peter about a story of the American Revolution, which wouldn't be so predictable seen from his very different point of view."

To make movies, and to wind up in Australia, O'Brien had first to quit what could have been a long career in the corridors of power in Washington, D.C.

"Politics is a very intense experience," he explained, finally returning to his somewhat abrupt departure from the Capital that Bicentennial year. "It was certainly the most intense of my life. I just wore out. The impeachment hearings were so intense that you had to ask, 'How do I top that?' And the answer was that you couldn't. When my friends heard that answer, they were good enough to say, 'Then now's the time to go.' "

Yes, yes, Mr. O'Brien. But would you mind telling us how you got to be a movie producer?