A few days into the battle of Iwo Jima, a squad of American troops raised a flag at the pinnacle of Mount Suribachi, the highest point of the tiny island. As a military victory, it didn’t mean much – the fighting would continue for weeks afterward; but it happened to be captured in a photograph that was rapidly dispersed by the nation’s papers. It didn’t matter that the actual details of the flag-raising had little relation to the version that was put out, or that half of those pictured were dead – the remaining three were shipped back to the States and presented as heroes, in a colossal media circus engineered to bring in funds for a war that was increasingly bankrupting its government.

Eastwood’s adaptation of James Bradley and Ron Powers’ book is undoubtedly worthy in its choice of material. Its focus is less on the battle of Iwo Jima than on the three marines – Rene Gagnon, John Bradley, and Ira Hayes – who were pulled out of the fighting for an entirely different kind of martyrdom. Eastwood leaves us in no doubt that, if these men were heroes or considered themselves as such, it wasn’t because they’d put up a flag. None of them were comfortable with their new role – as presented by Eastwood, it’s hard to imagine that anyone could be – and saw the process as a betrayal of the “real heroes”, alive or dead, that they’d left behind.

It would be unfair to say that Eastwood’s film is anti-war, although it frequently seems to want to be – and perhaps that’s the biggest problem with it, that it’s at once incredibly didactic and yet unsure of exactly what it has to say. Flags of our Fathers makes the same arguments over and over – that the marines weren’t fighting for their country but for each other, that their heroism was towards each other and not for some wider abstract ideology – but, as pertinent as those points are, they never gel into a consistent perspective. Perhaps, it says, there were no heroes after all, only young men trying to keep each other alive under appalling circumstances. But then, doesn’t that make them heroes? Similarly, Eastwood’s distaste at the use of the young marines to sell war bonds to a public sick of war is obvious – but he even-handedly reinforces the point that the alternative would have been a truce bordering on surrender.

It would be easier to swallow if his film didn’t seem to have been edited at random – it hops around between past and present, through different layers of memory, throwing in chunks of battle footage almost as footnotes. It’s not exactly confusing, but it does make for tremendously dull viewing. Whenever you’re drawn into one strand another abruptly takes its place, leaving you no time to get to know characters that have already been reduced to two-dimensionality by Broyles Jr. and Haggis’s script. Even the battle sequences, which given their scale should by rights be some of the best committed to film, are ham-strung by problems of perspective, not to say by overuse of special effects. One minute we’re with the marines on the beach, the next in a Japanese gun emplacement, and then suddenly the camera finds itself in the CGI cockpit of a CGI plane, leaving the baffling impression that the battle of Iwo Jima was some kind of gigantic computer game and fundamentally undermining every point the film is trying to make.

Flags of our Fathers suffocates under its determination to do everyone and everything justice, to tell the impartial truth about historic events that have already suffered from too much interpretation. The source material is undoubtedly interesting, as are the questions it raises, but the execution saps the life from the film at every turn. What could have been devastating is only likely to appeal to those with an interest in the history, and the rest of us can only hope that Clint’s follow-up – Letters from Iwo Jima, which offers the Japanese perspective on the battle – turns out to be the movie that this might have been.