Deep in the credits for the documentary Of Fathers and Sons comes a startling notation—a mention of the firm that supplied kidnapping and ransom insurance. That’s an indication of just how dangerous the project was for director Talal Derki, who risked his life to get inside a radical Islamist family in Northwestern Syria.

Derki posed as a filmmaker sympathetic to jihadi ideology to gain the trust of Abu Osama, one of the founders of Al-Nusra, the Syrian branch of Al-Qaeda. He spent two and a half years living in close quarters with Osama and his brood of children, including 13-year-old Osama and his brother, 12-year-old Ayman.

“Although I am an atheist,” Derki, a Syrian of Kurdish descent, has written, “I prayed with them every day and led the life of a good Muslim to find out what is happening in my country.”

The picture he paints is a disturbing and paradoxical one. Although Osama clearly loves his young sons—roughly eight of them populate the film—he loves the idea of establishing an Islamic caliphate more.

“He believes 100-percent in what he’s doing,” Derki tells Deadline. “And this is what I want to show, that people like him are super-believing. They are not fake.”

When Osama isn’t busy firing at foes with a sniper’s rifle, he defuses landmines and harvests the explosive material to sell to other bomb makers. When he’s at home, the kids learn at his knee. At one point, the boys are encouraged—perhaps in jest—to kill their cousin, a two-year-old girl, for failing to wear a hijab. In another scene, a son of about three tells Osama proudly that he has chopped the head off a bird, “like you did to that man.”

The father dreams of sending his offspring into battle in the future—“God willing,” he says.

“He’s ready to sacrifice them,” Derki notes mournfully. To prepare young Osama and Ayman for jihad he dispatches them to a training camp, where the boys and fellow campers sport camouflage fatigues and black ski masks.

“I witnessed the death of a lot of children who were involved in this war,” the director recalls. “They carried weapons even though they can barely hold them because they’re heavy.”

Ayman eventually returned to school—one of the few children of Osama père to seek an education. But to please his father, Osama fils shuffled dutifully down the warrior’s path, though he appeared ill-suited to it—a bit of a weakling who is beaten up by his younger brothers.

“If he was the son of anyone here [in the West] he would be an artist,” Derki maintains. “I know how sensitive he was. But because he grew up in this environment, you saw him throw stones at girls in the school.”

Of Fathers and Sons has earned Best Documentary nominations for the IDA Awards, Film Independent Spirit Awards and Cinema Eye Honors, a recognition of the unparalleled view it provides of life within a jihadi family. It has won awards from festivals around the world, including Sundance, where jurors saluted the film for providing “a terrifying experience of war.”

The physical and psychological impact of unremitting violence comes through forcefully in the film—in the haunted eyes of men captured by Abu Osama and his cohorts, as they grimly await execution. It’s felt in the wails of Osama’s children after their father returns home from one expedition badly injured, a foot blown off by a landmine (Osama orders his wife, heard crying off-screen, to silence herself).

At a recent screening in Los Angeles, Derki recounted that Osama’s jihadi friends assured him his missing foot would be waiting for him in paradise upon his death. Whether that reunion has taken place is anyone’s guess, but just last month news emerged that the dedicated extremist, not surprisingly, had perished in action.

“He got killed when he was dismantling a car bomb that was sent by another group. It exploded in his face. So he was doing his job,” Derki comments. “The film shows how his life is dangerous, how he really wanted to be martyred, so he got his request.”

Derki articulates multiple aims for his film, among them providing Western audiences with a more nuanced depiction of militants fighting under the banner of ISIS and Al-Qaeda.

“If you don’t understand your enemy you cannot defeat him,” the director states.

And he seeks to reveal the way many jihadis are formed—in a crucible of brutality where kids are emotionally battered, in thrall to all-powerful fathers who rule patriarchal societies.