After the premiere of Hell on Earth at the Tribeca Film Festival, an audience member asked filmmakers Sebastian Junger and Nick Quested why they had chosen The Fall of Syria and the Rise of ISIS, as the subtitle has it, as the topic of their documentary.

“It’s the greatest tragedy of our generation and we had to address it,” Quested told a crowd Wednesday at Cinépolis Chelsea.

This new documentary from the makers of the acclaimed Restrepo leaves little doubt about that, serving as a basic primer for the conflict that has taken some 400,000 lives while also putting a human face on the quagmire. Junger, best known for his book The Perfect Storm and his war reporage for Vanity Fair and The New Yorker, introduced the film thusly: “I hope you’ll be startled into an awareness of what’s going on over there, but also inspired by us humans.”

The inspiration comes largely from Radwan, a refugee of Aleppo who films his family while they’re bunkered down in Manbij as air strikes occur all around them. As their young children look on in helplessness and fear, he and his wife heatedly discuss how best to escape the loathed Assad regime– he wants to flea to Greece, but she’s afraid of losing her entire family at sea. Finally they make it to Turkey, filming their heart-pounding trip across the border. (You can see a mini doc about the family, using footage from the film, below.)

Junger explained that the Syrian refugee was the brother of Adnan Mohammad, an archeologist at the National Museum of Damascus who was interviewed for the film, for a segment dealing with the Islamic State’s plundering of antiquities. “[Adnan] told us that his family was recently displaced from Aleppo and we managed to get a camera to them and we gave them some instructions on how to shoot themselves,” Junger said. The move was in keeping with TV journalist Tim Sebastian’s philosophy of “trying to find humanity in the darkest places,” as Junger put it.

Once the family made it to Turkey, Quested went to meet them and film them shopping for smugglers to take them across the water to Lesbos, Greece. This was one of over a dozen two-week trips the filmmaker made during the film’s year-long production, to interview refugees, activists, intelligence officers, other experts, female Kurdish fighters, and members of the Free Syrian Army (Trump’s former national security advisor Michael Flynn even makes a few appearances).

All of this resulted in nearly 1,000 hours of footage. Quested used a hidden camera to film a dealer trying to sell plundered antiquities, and filmed oil trucks at the Iraq-Turkey border, for a segment showing how ISIS funds its operations. Such documentation can be risky, and at one point Quested was arrested while filming a pipeline near Kirkuk, Iraq. “I did enjoy the hospitality of the peshmerga for some time,” recalled the British filmmaker. “They were very nice– you drink a lot of tea and tell jokes, and try to find some common ground. Futbol is always a good one.”

In the end, Hell on Earth is very much about common ground. It portrays grisly ISIS killings while reminding us that the organization’s anger is fueled in large part by Western actions in Iraq and Guantanamo. What’s more, its public executions are nothing new, as the documentary makes clear via photos of lynchings in the United States. “While we were doing this, while we were researching,” Junger said, “I had this moment where I realized they’re doing this now but every society I could think of had done it at some point. And by ‘it’ I don’t mean just killing people, I mean taking them into a public square and torturing them to death in a way that everyone else would have to watch.”

The documentary also holds Obama accountable for threatening to retaliate if Assad used chemical weapons, only to back down when he did so– an about-face that discouraged and arguably endangered Syrian rebels. Not that the film advocates for such action. “Journalism means not taking a side,” Junger said.

So what can we do? That’s exactly what one audience member asked during the Q&A.”

“Things like this happen at such a scale that individual citizens in this country, I don’t think can do very much, actually,” Junger responded. But he pointed to an op-ed, published by Vanity Fair this week, in which he wrote, “A truly bold move by our president would be to establish an open-ended refugee program for any country where we are conducting military operations—including Syria.”

At Cinépolis, Junger told the crowd, “If we had an open-ended refugee program for countries where we waged war, we actually might conduct military operations in fewer countries and might be more hesitant or skeptical before going into countries.”

One has to wonder whether the president has read Junger’s op-ed, provocatively titled “How Donald Trump Could Stop Being a Coward.” On Wednesday, an audience member wondered whether the movie had been screened at the White House.

Quested responded, “Maybe if he sees it on Fox News first…”

“Hell on Earth” continues at the Tribeca Film Festival through April 30 and will be broadcast on the National Geographic channel in June.