For more than two years, Syrian-Kurdish filmmaker Talal Derki lived among fighters of the Al Nusra Front in Syria’s conflict-stricken Idlib. There, he was known as Abu Yusef Al Almani (Abu Yusef the German) and as far as the extremists knew, he was one of them. He prayed with them, ate with them and pretended to sympathise with their goals of establishing a caliphate to rule over the Levant. To their knowledge, he was there documenting the extremists’ way of life in a favourable light.

What he has made is an Oscar-nominated documentary called Of Fathers and Sons, a chilling and cautionary tale that details how hatred and fundamentalism is transmitted from one generation to the next. The documentary focuses on Abu Osama, a father who is preparing his two sons to join the terrorist movement.

“When they are old enough, I will send them into battle, if the Nusra doesn’t send them first,” Abu Osama is seen saying in the documentary’s trailer. His sons, Osama and Ayman – named after prominent Al Qaeda leaders Osama Bin Laden and Ayman Al Zawahiri – have different reactions to their upbringing. While Osama is eager to follow in his father’s path, Ayman longs to return to school.

The documentary screens at NYU Abu Dhabi’s Arts Centre on Monday, November 25, as part of CinemaNA, curated by the university’s Film and New Media Programme in partnership with Sorbonne University Abu Dhabi.

“Children are inherently innocent and impressionable. I am a father myself, so it was really difficult watching these children being swayed into the jihadist ideology. The first thing they were taught by the Nusra was how to wear a mask and conceal their identity. When asked for their names, they would reply that they had none. They were taught to be jihadists before they learnt how to be people.”

Besides facing the dangers of being in Idlib – a conflict zone being subjected to air strikes from several nations and coalitions – Derki also had his companions’ suspicions to consider. “Idlib was being constantly rocked by explosions. It was chaos. Russians, Americans, the regime and the countless factions fighting in Syria were all bombarding the area. But besides all that, I had to be careful not to accidentally reveal my true identity. If the Nusra found out that I was a secular Kurd, they would, without a doubt, have killed me. I was also in the constant company of a man who enjoyed being in danger. Abu Osama specialised in rigging vehicles with bombs so we were constantly surrounded by explosive materials,” Derki says, adding that Abu Osama, the main character of his movie, died in a car explosion in October last year.

Derki was inspired to work on the documentary after noticing a rise in fundamentalist thinking in his homeland. Prior to filming Of Father and Sons, he worked on another documentary, The Return to Homs – which won the Grand Jury Prize at the Sundance Film Festival in 2014 – and a few short fiction films. “My aim was to research the radical mentality spreading in Syria. I wanted to look into it, to understand it. The documentary is not about the war. The primary focus of the documentary is how children are being indoctrinated into extremist thought. The message of the story is not exclusive to Syria, either, there is a rise in radical thought across the world. I wanted the documentary to highlight the danger of this illness and to combat it using proper education.”

To get an accurate and intimate portrayal, Derki had to use a small film crew. “It was just me and a cameraman,” he says. “Even with such a small team, it took some time for the children to become used to a camera being in their presence. To not constantly look at the lens. We would have attracted too much attention if we had a fully fledged team. It wouldn’t be the same movie, either.”

When asked what aspect of living with the extremists was the most difficult to communicate, Derki says: “How long each day was. Especially when we didn’t seem to have anything to film. Those were the most difficult. There was nothing to keep me busy and I had to keep up the act, pretending I sympathised with the ideals they were raising their children with. There were moments when it all became too much … when I couldn’t take it any more.”

Towards the end of his time in Idlib, Derki’s cameraman had to leave the city and Derki had to find someone else to shoot the final five minutes of the documentary. “A Tunisian emir in Idlib was asking questions about us, and we knew our time was up. I just had one more scene to film – the one with Osama at the Sharia camp – and once I found a cameraman to shoot the footage, we decided that was it. We couldn’t stay there any longer.”

But for Derki, going back to Berlin wasn’t as easy as leaving it. Worn out and depressed, he had to go through a rehabilitation phase after returning from Syria. He also sought to strengthen his relationship with his family as a way to overcome the anxieties and fears that had built up during his time with the Al Nusra Front, who have since rebranded to Hayat Tahrir Al Sham.

“I had to go through a period of recovery. I went through a period of self-reflection where I contemplated my place in this universe and the road we are travelling together as a species,” Derki says, adding that he recently had his forearm tattooed, a symbolic gesture that marked the end of his time with the extremists.

“Not that I could go back even if I wanted to,” he says. “I’ve received death threats and was warned against returning to Syria and Turkey. I’ve made myself a target with this documentary.”

But for Derki it may all have been worth it. “I feel incredibly lucky with all the attention the documentary has received. It was screened in cinemas across the world and is now being featured in several European channels.”

Derki is now writing a series pilot for a US production company. Though he wouldn’t divulge more details about the project, he did say they were based on ideas and notes he had from previous projects.