For a German filmmaker tackling a film on this subject must have been a great responsibility.
I felt it much more while I was preparing the film. As soon as you shoot the movie, you deal with the responsibility in every set up, but you can't let yourself be carried away by that. It's a step-by-step process. But preparing it was really tough. And of course it's not a pleasant subject to deal with. As a civilised human being these are things you hate and detest. Nevertheless you have to dig deep and that's not pleasant.
Your first film, The Experiment, seems to foreshadow this one with its investigation of the worst excesses of human nature
If you look at Shakespeare, evil is everywhere. As sad as it is that seems to be the most powerful observation when it comes to the history of mankind, so as a director you deal with that. The Experiment was me working as a psychologist and if you look at Abu Ghraib, I don't think I was that far off.
Downfall was me being a historian, trying to combine that with my craft as a filmmaker to make it believable, although, of course, I had to stick closely to the facts.
Bruno Ganz seems frighteningly authentic as Hitler. Was he an obvious choice for the role?
That was something we came to realise after we took this black-and-white photograph of Bruno and drew the strange haircut and moustache and wrinkles around his mouth. It was shocking how similar he looked. It was even more shocking to see him in the uniform with the make up on. He was shocked as well, but that helped convince him to do it. He was the only one actor we had in mind.
The taboo you have broken in this film is in portraying Hitler as a human being, not a slavering monster.
It seems to be, although I've never understood that approach. Why would you create a myth around this man? That's the last thing he deserves. He's the worst mass murderer in the history of mankind and the most monstrous thing is that he is human; he deliberately did what he did and knew exactly what he was doing. The man was not insane. He had a clear plan, which meant murder and destruction. That's the way we had to deal with it.
There is a discomfort when you realise that Hitler might, in other circumstances, have turned out like any one of us.
As Germans we have a responsibility to deal with our own history. We will always have a responsibility for what happened. Of course, I'm not guilty. I was born after the war. But as a German, I have to deal with that responsibility. And it will go on for hundreds and hundreds of years. We can't get away from it. So we have to start asking all these questions and undergo this painful process of investigation, examining the background to it. I think the film works as an inducement to do just that.
What was the experience of your own family during the war?
My father was 15 when they drafted him in 1945 to man anti-aircraft guns. He couldn't care less about all that. He was more interested in chasing girls. With my mother it was different. She was a member of the Bund Deutscher Madel, which was the Nazi youth organisation for girls. She very much believed in this ideology. She believed in Hitler as their hero. She enjoyed her time with all the other girls, because they were sent out into the country. The way she talked about it they were having a ball. For her it meant freedom. It came as a shock when the Americans came and destroyed the portraits of Adolf Hitler, explaining how bad this man was. As a matter of fact, her talking about that time triggered my interest in it when I was about 12, or 13. I started reading practically every book I could get my hands on.
The bunker you recreated for the film seemed incredibly claustrophobic. Was it?
Certain rooms were very unpleasant to be in, but others were okay. They were all built in a studio. And the set was constructed in a very solid way. It was like a submarine. You had to walk in from certain ways and then you had to go through rooms to get to the rooms that were on the other side. It felt pretty close to what it must have been like then. And of course we were hot, because there were ceilings we could not take out. I think that very much enhanced the atmosphere and the performances.
In a film of many remarkable scenes, the one in which Magda Goebbels kills her own children is particularly harrowing.
I used that scene as a metaphor for the industrialised way of killing people, one by one by one. As painful and long as it is, I felt that scene had to be in there because it stands for the monstrosity of that crude concept. It was absolutely necessary.
How do you direct a scene like that, especially with your young actors?
If you work with children you have to be very honest. You explain the situation, that this hardly ever happens - parents killing their children - and to make sure that it does not happen again we are re-staging the whole thing as a bad example. Of course, then it had to be as believable as possible, but for them it was a game. They went for it.
For the adults it was terrible. Unbearable. I'm the father of two children and Corinna (Harfouch, playing Magda) has three children. It was terrible, because Corinna and Uli (Matthes, playing Joseph Goebbels) and some others started crying. We had to make sure that the children did not realise this. We got them out and calmed them down, and then did the scene. It went on for hours and hours.
On one side you were dealing with yourself being on the verge of tears, dealing with your crying actors, and on the other you're being a clown for the kids. That's very tough.
Downfall is out on DVD in the UK on 19 September