The performances and the emotions you got from those horses must have been very satisfying. Can you talk about that?

I want to believe that the horses knew exactly what they were doing and performed those parts the same way that Emily Watson or Peter Mullan did. They were all performers. There were times in the movie when I wouldn’t even tell the horses what to do. They’d be in a scene and would be reacting in that scene in ways I couldn’t imagine a horse would be able to react or act. And there are times you just have to sit back and thank your lucky stars that the horses somehow were cognizant that something was required of them that none of us could tell them, but they intuitively were able to give it to the moment in the scene.

Without spoiling anything, there’s a moment toward the end of the story, just as an example, where they’re leading Joey to some place that Joey wants to go to. And right at the end of the scene, Joey nuzzles Albert with his nose, pushing Albert as if to say, “Okay, I’m ready to go. Take me there.” That’s nothing we could plan for. How the horse knew that it was the last line of the scene and it would be wonderful for him to give the boy a little nudge, I don’t know, because nobody trained the horse to do that. The horse just took his own cue, and that’s in the picture.

Did your British crew and cast members come to you with personal stories about their relatives in the Great War?

Yes, they all had relatives who fought. The British crew constantly told me stories about their grandparents and great grandparents who had fought in the Great War. They all knew their stories. They had been passed down from generation to generation. It’s a war that’s kept alive in the finest European traditions of being really up on your history. We don’t have the same kind of due diligence here in this country with our young kids. But in England, it’s just handed down. Parents, grandparents always talk about it. So, I was the beneficiary of these great stories of personal heroics and just the tedium of being in a trench war for four years.

How did the ensemble cast work together?

War Horse isn’t the story of just a boy and a horse. War Horse is the story of so many different people. And this is one of the happiest ensemble casts I think I’ve ever been able to work with. It’s an ensemble cast where the characters never really appear in the same scenes with each other and yet you’re left with the impression that they were all in this together. I’m really proud that so many good actors gave so much of themselves to us yet never got the chance to act with each other.

War Horse will be released in cinemas on 13 January

Interview: Steven Spielberg