At the moment, the box office is besieged with epic combat. All those actors, extras, and special effects are passionately brawling for the survival of Middle-earth in the final ''Lord of the Rings'' installment. Tom Cruise is turning his back on America to fight with Japanese warriors in ''The Last Samurai.'' And ''Cold Mountain'' is full of glimpses of the Civil War and its ravages. Yet it's the 95 minutes spent listening to former defense secretary Robert McNamara explain his notorious roles in World War II, Vietnam, and the Cold War that offer both blood-quickening intensity and the lasting chill of relevance. ''The Fog of War'' consists of interviews of the then 85-year-old McNamara by filmmaker Errol Morris, though their conversations often feel more intimate and surreal than a director prodding his subject. With Morris somewhere off-screen, McNamara is seated alone, in a somber but overlit and undefined studio space, gazing into the camera, his face etched into a pleading, anguished sadness. He's in confession.
The movie offers McNamara's recollections of serving under Air Force General Curtis LeMay and in the Kennedy and Johnson administrations. In McNamara's rear view, victory might mean never having to say you're sorry. He recalls LeMay wondering, in the haze of their ghastly 1945 firebombing campaign over Tokyo, ''What makes it immoral if you lose and not immoral if you win?'' McNamara weaves between those sorts of rhetorical deductions and a hard-won if hardly comforting wisdom, usually to Morris's own surprise and consternation.
''The Fog of War,'' in fact, has a subtitle, ''Eleven Lessons From the Life of Robert S. McNamara,'' and accordingly, the film is divided into tutorial chapters whose effect is not unlike that of sitting in the classroom of a professor you despise.
Amazingly, though, Morris affords McNamara the opportunity to disarm you. Yes, the man a journalist once called ''an IBM machine with legs'' is still a wizard at detachment and compartmentalization. Yet his sharp, straight talk and borderline remorse have a sort of humanizing charm, even as anyone with the barest knowledge of McNamara's past would know he probably makes the grade as a war criminal.
McNamara's combat strategies were cold. That coldness, however, was something he recognized and apparently struggled with, surrounding himself with feeling humanists to make up the emotional difference. He expresses a fierce admiration of Kennedy's rationality and compassion, and he was seemingly transformed once Johnson assumed power. Without Kennedy, it seems, McNamara was without a warm checkpoint for his remoteness. Indeed, he left the Johnson administration in 1968 over the escalating situation in Vietnam, but refused to speak out against his former boss or the war.
Fiercely reticent even after hours and hours of interviewing, McNamara can be frustrating, like a door that opens onto a brick wall. In his willingness to speak up but not entirely out, McNamara provides the movie with its key fascination: the confessor who refuses to comment. ''To do good you have to be willing to do evil,'' is the closest he'll come.
Morris studied philosophy at Berkeley (like McNamara, incidentally) and protested the Vietnam War, making McNamara a natural subject for one of his interrogations. Yet until the film's epilogue, in which McNamara appears to be dodging further inquiry and Morris's cameras, ''The Fog of War'' isn't quite angry with McNamara. It's sometimes sympathetic and, on several occasions, grimly whimsical. (In one scene, bombers drop numerals from the sky accompanied by Philip Glass's mischievous score.)
In fact, on a first viewing you may leave crestfallen by how ambivalent and clinically ambiguous the movie seems. Fog is the dominant psychological and ideological motif, but why does this great but fallen man deserve such a seemingly unmitigated self-defense? Where is Morris's counterpoint wrestling with McNamara? Where is McNamara's wrestling with the truth?
After a second sitting, you realize that the film's central drama is not between the former secretary and the filmmaker. It's between McNamara and history.