Flags of Our Fathers (15) <!-- none onestar twostar threestar fourstar fivestar -->

Age brings wisdom, we like to hope, but in the case of Clint Eastwood it has also brought an amazing rejuvenation of creative energy and daring. Twenty years ago, Eastwood directed and starred in Heartbreak Ridge, an American Marine movie of such staggering fatuousness and dishonesty that even his fans (like me) believed he had finally shot his bolt. How wrong we were. Since then, a handful of duds aside, he has given us Bird, Unforgiven, Mystic River, Million Dollar Baby and, his most underrated film, The Bridges of Madison County (gold panned from the dross of a potboiler). Now, in Flags of Our Fathers, he has made an American Marine movie that not only atones for the earlier one but investigates the whole genre as an engine of propaganda and PR.

Just as Unforgiven repudiated the glamour of gunslingers in the Old West, so Flags of Our Fathers puts the facile notion of "war heroes" under scrutiny. It is developed as the story of a photograph. During the ferocious battle for the Japanese island of Iwo Jima, a vital enemy stronghold in the Pacific War, five Marines and one Navy Corpsman raise an American flag on a captured mountain. A photographer, Joe Rosenthal, happens to catch the moment, and within days his picture has become a front-page icon of warrior fortitude - and a beacon of hope to an exhausted nation. The authorities are quick to capitalise on its impact, and summon the surviving flag-raisers back to the US in order to front a fund-raising campaign on behalf of the beleaguered war effort. These Marines have taken one mountain, now they have to help take another - "a mountain of cash".

What follows is a careful, and painful, reckoning of reality against myth. Eastwood is all too aware of how war has been Hollywoodised (having famously contributed to the misrepresentation during his own career) and his young Marines start out as impressionable as anyone else: the names of Cagney and Tyrone Power are jokily bandied around while they prepare for the Iwo Jima invasion. To heighten this ironic contrast, the film's writers, William Broyles Jr and Paul Haggis (adapting from the book by James Bradley), keep shifting between the gaudy PR exercise into which the three survivors have been dragooned and their traumatised memories of what happened on the island's volcanic slopes. Herded around as poster boys for Victory in Japan, medic "Doc" Bradley (Ryan Phillippe), shy Native American Marine Ira Hayes (Adam Beach) and Rene Gagnon (Jesse Bradford) find themselves at odds with their unsought celebrity. Ira becomes a tormented drunk, Rene decides to see it as a career opportunity, and Doc, the sanest of them, withdraws into remorse: "It's hard enough to be called a hero for saving a life," he says, "but for putting up a pole?"

What none of them can explain to the folks who clap and cheer them is the horrific nature of their experience on Iwo Jima. As the massed cavalcade of boats disgorge the soldiers on to the shore, we are braced for an almighty onslaught of violence - which duly arrives. Hand-held shots of men running and ducking while raked by machine-gun fire alternate with the monstrous roar of cannon-fire targeting tanks, ships and whole swathes of ground. The colours of this open-air slaughterhouse - ash-grey and khaki punctuated by sudden starbursts of blood - the jittery editing and impossible volume unavoidably recall the Omaha landings of Saving Private Ryan, the film that created a new benchmark in battlefield realism. Not to take anything away from Spielberg, who's a co-producer here, but he was directing Ryan at the age of 50; Eastwood has taken on the job at 76, an age when most pensioners would do nothing more strenuous than walk the dog and choose from the Early Bird Special. What's even more remarkable is that he has made a companion film, Letters from Iwo Jima, about the same battle, as seen from the Japanese point of view. It will be released next year.

The scale and technical achievement of such a project will be to Eastwood's lasting credit. If a fault can be picked, it's one intimately entangled with the story itself. Almost from the moment the flag-raising photograph is published, controversies gather: one of the six soldiers is misidentified, bereaved mothers believe they have spotted their son in the picture, and a rumour emerges that the photographer staged the whole thing. (The truth is that the photograph was of a replacement flag, the original having been spirited away lest it fall into the hands of a booty-seeking general). The problem is that we, as audience, aren't quite certain who's who in the platoon, let alone in the photograph: the ubiquitous khaki and helmets don't help in identifying individuals. You'll notice Jamie Bell (from Billy Elliot) and Barry Pepper (Saving Private Ryan), and a handful of others, but amid the wholesale carnage it's hard to know which particular death we're meant to be mourning. Eastwood was perhaps determined not to emphasise the casting, but it leaves his film a bit short of character.

Is there a contemporary resonance in the film's disdain of glib triumphalism and governmental duplicity? It could hardly be otherwise. But Eastwood, always his own man, is not delivering a polemic, however aggrieved he feels on behalf of his subjects. A poignant air of remembrance hangs over the film, which begins with a veteran of the battle recalling his fallen comrades; his testimony, and others', serves to sharpen the point that these young men had no thought of becoming heroes, they were simply hoping to make it through with their friends next to them. As Hayes says: "All I did was try to not get shot." This decorous film reminds us that even survival can be a mixed blessing.