The Vietnam War has been well explored in film, though rarely even-handedly. What is different about your approach?

I wanted to tell an aspect of Vietnam that had not been told before. Most of the men who went, went for the best of reasons. What we think of as a Vietnam-era film is men killing babies, raping civilians, or napalming innocents. What has not been emphasised is that was not the majority of experience. The book is about a man who said to his troops that he would be first to set foot in the field but the last one off and won't leave till every one of you is off - dead or alive, and he does that. That story is timeless and not applicable just to the Vietnam War.

What attracted you to the story?

This story had powerful emotions, physical drama, and lasting meaning. In the wake of September 11, America uses the word 'hero' to apply to almost everyone who had anything to do with that date. There are certainly many heroes, but we use the word readily. The men in this unit who went in 1965 to fight communism, believed as much that they were fighting evil as the soldiers who went to Afghanistan last year. Yet, the men who came back from Vietnam were treated as villains. There is a sense of injustice.

This is a far more emotional movie than "Braveheart" or "Pearl Harbor".

With "Braveheart", I was essentially recreating the legend. In "Pearl Harbor", I had an event around which I created fictional characters. For this story, I could not create events, nor could I create characters. Not only because many of the people are still alive. Soldiers are always betrayed by politics - I could not allow them to be betrayed again through an accusation that I had let politics shape the story. I wanted to say unambiguously: this is what these men did. This is not a political movie.

Do you believe "We Were Soldiers" can ease prevailing shame about Vietnam?

My hope is that it will help heal wounds left by that war. And that those who heal the most are those who were wounded most. September 11th reminded us that there is evil in the world, as well as duty, honour, and country. I want it to be a healing and uniting experience. People who said 'get our boys out of Vietnam', and those who said 'let's support our boys in Vietnam', can join hands and say Amen at the end of this.