In his award-winning 2013 film "Return to Homs," the Berlin-based Syrian director Talal Derki took viewers into the midst of a fight for democracy turned civil war without end. His latest film, "Of Fathers and Sons," which recently premiered at the Sundance film festival where it won the World Cinema Grand Jury prize, returns to war-torn Syria and offers a rare glimpse into the life of an Islamist fighter's family.

Living for two years with a Nusra Front "soldier of God" in a small village in northern Syria, Derki focuses his camera on the boys being trained to follow in their father's footsteps and become jihadi fighters. Here the horrors of war and the intimacy of family life are starkly intertwined, as Derki explains in an interview with DW.

You spent more than two years shooting your documentary film in the Idlib region in northern Syria, which then was controlled by the Nusra Front (now  part of theTahrir al Sham coalition). You were hiding your real name and your intention as a filmmaker. You made Nusra fighters trust you and closely followed their daily lives close to the frontline. Why did you decide to take such a high risk?

You know, my life before these bad times was different. I was living in Damascus. I studied cinema in Greece. Most of the people I knew in Damascus as a filmmaker were artists, you know, we never were in touch with the religious people, and by saying religious I am talking jihadis, salafists, those were very rare in Syria. After the revolution started, I filmed my documentary "Return to Homs" in Syria, with people who were into democracy and freedom. During the time of the shooting people started to talk about a "caliphate." It was the month when IS [eds.: the so-called "Islamic State"] declared itself, in Spring 2013. I witnessed how many people loved them, so much brainwashing! That was for me the biggest shock.

During the last block of shooting for the film in 2013, I met for the first time a jihadi from IS in the desert north of Homs. I was there waiting, and the only people with internet access were IS. So I met some people and later I thought, you know, I have the possibility to do it, I have access. I believe it's difficult for someone else to do this. So it has really been a big journey since we started in 2014.

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How was it possible for you to hide your past from the Islamists, to hide who you really are?

They didn't have much knowledge about my background. I had hidden all information, had avoided all photos of me drinking alcohol and being with girls. And before I didn't write any article against the jihad. So there was no clash. I also gave some interviews on opposition Arabic radio and TV that supported them, and they were happy thinking this is a guy supporting us. And I told them I was motivated by their movement, I wanted to learn from them.

Your documentary mostly has a "fly on the wall" perspective. The people in the film seem to forget the camera, the cinematographer (Kahtan Hassoun) is in "observational mode." You accompany the family of a Nusra Front fighter at their home and follow the father to the frontline without any commentary or voice over. Can you explain this approach?

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I wanted to go psychologically inside the society of the jihadis. I wanted to understand how it happened, how they become what they are. Who are these people? How do they look from the inside? What are their codes? How do they brainwash people? To understand how they convince people through the story of the new generation. And the film is also about a father's legacy of violence. There's a lot of violence, so what happens to the kids? In a way, I believe that every father can watch this film and find himself or his father somewhere inside it. I tried to capture moments that are eternal moments.

You spent more that two years with the Nusra Front family. How did you manage to maintain your alter ego for so long?

It's a matter of day by day. You have to forget who you are. You have to be a new person to make such a film. There was no other option. I had to do this. Firstly for my safety. Secondly to observe, to go to their point of view. To understand what their life looks like. You need to let them trust you. I also tried mostly to reduce the places where you shoot, and I filmed a lot inside the house.

When I went with the father outside, he always met with other jihadis from other Arab countries and from Europe, and these are dangerous people because they don't easily trust you filming them, whatever your background. And they have experience researching online. When they investigated me, I had to tell I am a war photographer. And also from the outside I had to be exactly like them. So I was praying with them, listening to them, shaking my head like them.

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How is your very personal approach to making this film a result of your own experiences in Syria?

I learned from my father that to tame your nightmares, you need to capture them first. It's about getting them out from the subconscious to the conscious. Write it down. Write it with a camera and then leave it there. That's what I did.

One of the boys featured closely in the film is Osama, who is named after his father's hero, Osama bin Laden, and who leaves for the Sharia military camp at the end. What was Osama like?

He is very sensitive and rebellious. Osama is the one who lied to his father that he prayed, but he did not pray. And I know him. If he grew up in a different family, he would be an artist. I am sure.

If the society was strong in that region, if there wouldn't be violence against kids and women, if women were equal there, if there was a clear law about what children learn, the jihadis would not be able to find a place, nobody would welcome them. Look at countries like Iraq, Afghanistan, Syria, Libya — violence will bring more violence, will bring more radical people. And this will go on.