THEY DIDN'T HAVE to make up too much for "Thirteen Days," the movie that tells the story of the Cuban missile crisis. The truth was juicy enough on its own. After all, what could be more riveting than the possibility of global nuclear destruction?

When U.S. spy planes reported the sudden appearance of Soviet nuclear missiles on Cuban soil in October 1962, that possibility loomed exceedingly large.

But the filmmakers did take some liberties. The most obvious example: the role played by Kenny O'Donnell (Kevin Costner) in the crisis. Although he was an adviser to President Kennedy, he did not figure as largely in the actual Cuban missile crisis as the movie implies.

"There's no evidence that he played any such role," says Graham Allison, a professor of international affairs at Harvard and author of "Essence of Decision," a thoroughgoing book about the Cuban missile crisis. He was also a consultant for the film. "This is an invention, encouraged a little by O'Donnell's own recollections. Many people remember about historical events that they played a bigger role than they did."

"If you see the movie as a step in the direction of history," says journalist Marvin Kalb, a Moscow political correspondent during the crisis, "then it is jarring for those who know Kenny O'Donnell played no role whatsoever. He was not one of [JFK's] advisers, was not that close to him. He probably knew something important was going on. I remain convinced that O'Donnell had no purpose whatsoever."

Counters "Thirteen Days" producer Peter Almond: "There's no doubt [O'Donnell's] portfolio did not include foreign policy or national security affairs. But O'Donnell did have an adjoining office to the Oval Office, was a member of JFK's ExComm [Executive Committee of the National Security Council] and did attend meetings at the president's request.

"The thing is, no one knows" everything that was said, or who said it, Almond says. "While there is a taped record of a number of the ExComm meetings, there were also plenty of discussions in small groupings -- a floating discussion in and out of the more formal sessions . . .

"We do know from memoir accounts, that [Kennedy] expressly asked O'Donnell to be at all the meetings where the president was in attendance and offer candid comments in private afterwards."

Which gave the filmmakers a fair amount of free license. However, that is not a freedom they took lightly, he says.

"We can't hide under the shield of artistic freedom if we're going to play hard and fast with important events," he says.

Although it was dramatically necessary to compress principal characters and put the words of others into their mouths, they made sure the essential truth was preserved. Screenwriter David Self drew on numerous historical sources, including White House tapes, memoirs, oral histories, CIA documents and personal interviews. He also listened to hours of interviews with O'Donnell, conducted by NBC White House correspondent Sander Vanocur.

"There was a serious awareness on our part of not speculating too far afield, or interpreting too widely these events," Almond says. "At the same time, of necessity, we compressed certain events for efficiency's sake. After all, we were trying to contend with 13 days of activity, incorporating events that precede those two weeks."

Another historical inaccuracy in the movie, according to author Allison, is the notion that the right wing contingent tried to maneuver the Kennedy brothers into nuclear war.

"That's inaccurate and misconceived. The most incredible element is the notion [in the movie] of O'Donnell calling [Air Force] pilots and persuading them to lie to their chain of command. That's [factually] a negative."

But some of the most dramatic -- even melodramatic -- moments in the movie, it turns out, are not made up. At first, it seems like liberal manipulation when (in the movie) the hawkish Air Force Gen. Curtis LeMay (played by Kevin Conway) characterizes the Soviets as a "red dog" in America's back yard that needs to be killed.

"You're in a pretty tough fix, Mr. President," he snaps impertinently at one point.

Kalb and Almond both contend that LeMay's characterization is accurate.

LeMay, says Kalb, was "representative of a group of very strongly anticommunist military leaders who believed that the only language that the Russians understood -- in the movie, this statement is put in the mouth of Dean Acheson -- was the language of force."

And this is one movie, at least, in which the filmmakers (including director Roger Donaldson) did not rush to use every bit of hyperbole they could lay hands on. According to Almond, one scene -- in which the Joint Chiefs of Staff exchange meaty profanities about the president when he walks out of the room -- was cut from the movie, even though it was taken directly from transcripts of President Kennedy's White House tapes during the crisis.

"It was so over the top in its impact, so loaded," Almond says, "as if to suggest we were making them look bad."

At the end of the day, Kalb says, "there's a larger question you're obliged to answer: For the people -- and there are many -- who know nothing or very little about the Cuban missile crisis, does this movie give you a basic appreciation of the seriousness of the crisis and the moment? I think the answer is 'Yes' in my judgment."

"The high marks I would give to the film," concludes Allison, "are for [conveying] the central truths of the crisis, including the real risk of nuclear war, the impossible and equally unattractive options, the high level of uncertainty and complexity about the decisions and, ultimately, the role of leadership on the part of the president."

-- Desson Howe