Ambitiously tackling his biggest canvas to date, Clint Eastwood continues to defy and triumph over the customary expectations for a film career in "Flags of Our Fathers." A pointed exploration of heroism -- in its actual and in its trumped-up, officially useful forms -- the picture welds a powerful account of the battle of Iwo Jima, the bloodiest single engagement the United States fought in World War II, with an ironic and ultimately sad look at its aftermath for three key survivors. This domestic Paramount release looks to parlay critical acclaim and its director's ever-increasing eminence into strong B.O. returns through the autumn and probably beyond.

Conventional wisdom suggests directors slow down as they reach a certain age (Eastwood is now 76), become more cautious, recycle old ideas, fall out of step with contemporary tastes, look a bit stodgy. Eastwood has impertinently ignored these options not only by undertaking by far his most expensive and logistically daunting picture, but by creating back-to-back bookend features offering contrasting perspectives on the same topic; the Japanese-language "Letters From Iwo Jima," showing the Japanese side in intimate terms, will be released by Warner Bros. next year.

One way to think about "Flags" is as "The Man Who Shot Liberty Valance" of this generation. That 1962 John Ford Western is famous for its central maxim, "When the legend becomes fact, print the legend," and "Flags" resonantly holds the notion up to the light. It is also a film about the Greatest Generation that considers why its members are, or were, reticent to speak much about what they did in the war, to boast or consider themselves heroes.

Skillfully structured script by William Broyles Jr. and Paul Haggis throws the audience into the harrowing action of the Iwo Jima invasion as a personal memory that can never be softened or forgotten. But the brutal fighting is eventually juxtaposed with the government's use of the celebrated image of the Marines raising the flag on Mount Suribachi for propaganda and fund-raising, with scant ultimate regard for the "heroes."

Reflecting its origins in the bestselling 2000 book by James Bradley (son of one of the central figures) with Ron Powers, tale is framed around a son's search into the wartime exploits of his father John Bradley, one of the six men pictured raising the flag. The I.D.ing and matching of some old-timers to their younger selves is never the easiest thing to do, and the same goes for getting all the names immediately straight for a bunch of young soldiers wearing identical uniforms and very short hair.

But the camera focuses on a handful of the 30,000 troops that landed on the inhospitable spec of volcanic ash and tufa that is Iwo Jima on Feb. 19, 1945, to dislodge some 20,000 well-fortified Japanese.

Among the men are John "Doc" Bradley (Ryan Phillippe), the only Navy man in a group that otherwise includes Marines: Rene Gagnon (Jesse Bradford), Native American Ira Hayes (Adam Beach), the highly capable leader Sgt. Mike Strank (Barry Pepper), Hank Hansen (Paul Walker), Ralph "Iggy" Ignatowski (Jamie Bell), Harlan Block (Benjamin Walker) and Franklin Sousley (Joseph Cross).

Such is the carnage at the initial landing (the Americans suffered 2,000 casualties that first day alone) that there will be some temptation to compare the scene to current co-producer Steven Spielberg's justly celebrated D-Day invasion sequence in "Saving Private Ryan." But Eastwood does it his own way, impressively providing coherence and chaos, awesome panoramic shots revealing the enormous armada and sudden spasms of violence that with great simplicity point up the utter arbitrariness of suffering and death in combat.

The visual scheme Eastwood developed for the picture is immediately arresting. Perhaps taking a cue from the island's black sand, as well as from WWII's status as the last war shot, from a filmic p.o.v., in black-and-white, pic is nearly as monochromatic as anything shot in color can be. Dominated by blacks, grays and olive greens, cinematographer Tom Stern's images have a grave elegance, a drained quality that places the events cleanly in history without diminishing their startling immediacy.

On the fifth day of fighting, some Americans reach the summit where a great deal of the Japanese firepower is concentrated, and six Marines plant a small stars-and-stripes. Shortly after, a larger flag is sent up and, in an event only shown in the film considerably later, six different men, Bradley, Gagnon and Hayes among them, responding to a photographer's half-joking question of, "O.K., guys, who wants to be famous?," put their muscle behind pushing up the new flag held in place by a heavy length of pipe.

At once, AP photographer Joe Rosenthal's shot became arguably the most iconic image of the American war. No faces were identifiable in the photo, leading to some confusion as to who was even in the shot, and three of them were killed soon after.

But the surviving three are spirited back to the mainland to spearhead a final war bonds drive. Bradley, Gagnon and Hayes are treated like gold-plated heroes everywhere, all the while being confronted by replicas of the flag raising made of papier-mache or even ice cream.

Of the three, Gagnon embraces his sudden celebrity, gallivanting around with his fiancee and expecting great things to stem from it. Already haunted by the horrors he witnessed, Bradley copes in a subdued way. But Hayes, whose story was dramatized onscreen in 1961 as "The Outsider" with Tony Curtis, of all people, portraying the Pima Indian, can barely hold it together.

Feeling from the outset that their participation in the tour is a "farce," that the real heroes are the guys who died or are still out there fighting, Hayes drinks heavily, embarrassing himself while having to stomach the everyday casual racism of being called "chief" or being refused service.

And once they've done their bit raising billions for the government, they're left on their own to put their lives back together. It's not an easy road, particularly for Hayes, who in one moving, genuinely Fordian moment, treks a long distance for a brief visit with the father of one of his fallen comrades.

Given this dramatic, wrenching arc, Hayes' story becomes the heart of the movie, and Beach, who previously played a Native American in the Pacific campaign in "Windtalkers," unquestionably takes the acting honors with it, delivering a full sense of the character's pain and sense of entrapment in an absurd situation. Other perfs are thoughtful, credible and deliberately unspectacular, although Pepper supplies special power as the leader the young men need as they come face to face with the enemy.

The director and editor Joel Cox find an effective and comfortable rhythm for the drama's parallel tracks. Spectacle is by no means limited to the battle scenes; one major setpiece is an enormous rally at Chicago's Soldier Field where the men are expected to scale a large model of Mount Suribachi and plant the flag. Perhaps the most felicitous of the film's many outstanding visual effects is the elimination of the recently built flying saucer-like addition to the venerable stadium.

The film's themes are so thoroughly embodied in the drama as it's told that there is no need for explicit statement of them, which makes the final bit of narration about the nation's need for heroes seem unnecessary. Another minor flaw is a Hollywood backlot look to a couple of Chicago street scenes.

Otherwise, "Flags of Our Fathers" is exemplary in its physical aspects. Combination of exteriors shot on the black beaches of Iceland with CGI work conveys a vivid and comprehensive feel of the godawfulness of Iwo Jima.

This and the forthcoming "Letters" represent the final work of the late, great production designer Henry Bumstead; no one could wish to go out on a better note. Pic is dedicated to him and two others who died during production, Eastwood's longtime casting director Phyllis Huffman and flag-raising photographer Rosenthal.

The director himself composed the spare, effective musical score.