Matthew Heineman had barely left one war when he found himself entering another. Making the publicity rounds with his 2015 film “Cartel Land,” centered around the brutally violent drug trade in Michoacan and people on both sides of the U.S./American border who made it their business to combat it, Heineman had been reading up on the ongoing strife in Syria, looking for a way to tell of one of the greatest humanitarian crises of our time as a result of the rise of the jihadist Islamic State. Yet when the filmmaker came across an article in The New Yorker about the citizen journalist outfit Raqqa is Being Slaughtered Silently, he realized that the war he would cover would not be fought with bullets, as much as the men and women who file dispatches from ground zero risk their lives, but instead with information as he followed the network built by RBSS to share their testimony with the rest of the world to rival the propaganda machine created by ISIS to recruit new soldiers from inside the country.

Heineman never actually stepped foot in Syria for “City of Ghosts” – as the filmmaker notes, he would’ve been killed instantly as a Westerner. But nonetheless, he is able to bring new perspective to what’s happening there through footage captured by RBSS and eventually following three key figures in the organization — Aziz, Mohammad and Mahmoud – as they leave the country to set up a relay system to bring coverage from Raqqa, which the Islamic State has cut off from all forms of media except their own propaganda channels, globally. With correspondents documenting the executions and random detentions that have made daily life a living hell inside the country, “City of Ghosts” not only demonstrates the collective power that emerges as a result of the coordination from within safe houses in Berlin and Turkey and clandestine transmissions from the streets of Syria, but conveys the frustration of doing such important work at a distance, as those exiled from the country draw strength from allowing others to witness the carnage going on in the region but are limited to helping friends and relatives in peril from behind a computer.

Heineman faced considerable challenges himself in making “City of Ghosts,” finding a way to capture the covert operation in action without endangering them and sifting through hours and hours of horrific ISIS propaganda videos – one of the film’s major revelations, in surfacing the flashy, sophisticated snuff videos featuring real civilian executions aimed at luring young men weaned on ultraviolent video games such as “Grand Theft Auto” to the cause — to give audiences from outside of the Middle East an idea of just what RBSS and the rest of the civilized world is up against. After a celebrated theatrical run this summer, the film was recently made available on Amazon Prime and Heineman spoke about finding the cinema in a story where action largely takes place in online communication, fusing together footage shot by RBSS and himself into an energetic and engaging narrative and watching these brave journalists get their due as the film reaches a larger audience.

A scene from Matthew Heineman's "City of Ghosts"How did this come about?

I had been reading a lot about what was happening in Syria and then came across this article in the New Yorker about this group “Raqqa is Being Slaughtered Silently.” Right when I read it, I knew this is my way into this story and I reached out to them through the Committee to Protect Journalists. Two of them happened to be in DC [when I was], so I got on the train that night and went down to meet them. At first, I think they were a little reticent about taking part in the film, but then they watched “Cartel Land” and called back and said, “Let’s do it.” I started filming them about a week later.

Since you dove right in, did you have an idea of what this was going to be – a film about the information wars more than physical warfare?

I was fascinated intellectually by this war of information – this war of propaganda – between ISIS on one hand and this group on the other, but I like to keep an open mind as to what the story is. This is also an immigrant’s story, about a group of people seeking refuge, and a story about rising nationalism in Europe. It was also about the cumulative effects of trauma, so the film evolved into many more things than just the story of RBSS versus ISIS.

You see the challenges of RBSS coordinating how they bring information to the public, so what was it like for you to figure out the logistics of coordinating a shoot?

The logistics were quite difficult. I was filming a group of people who are in various stages of exodus from Syria that didn’t necessarily want to be located, who are disparate in disparate locations, none of whom were ever really together. It was definitely the hardest film I’ve ever made [with] the coordination of being with different people at different times and figuring out who my main characters were and then trying to develop a rapport with them as I was doing this.

A scene from Matthew Heineman's "City of Ghosts"Did it immediately coalesce around these three guys in particular?

In the edit room, we were focused on those three, but there are many amazing members of the group that all have fascinating stories. I really wanted to make it very personal and very intimate [because with] some of these large issue films, not to put it in a box, but [they’re] often relegated to talking heads and to stats and it’s my belief that humans connect to humans. The more you feel for somebody, the more you care about them and the issue itself. So hopefully after watching [“City of Ghosts”], audiences have a little bit more empathy first and foremost for the members of this group, for the people of Raqqa, for the people of Syria and for immigrants all across the world, who have been forced to flee places like Raqqa.

There’s a clear point in the film, probably 30 minutes in, where it goes from being a film about the the past of RBSS to following them in the present. Did you know what that first half-hour would look like in order to know what to capture for the rest of the film?

It’s actually 19:33. [laughs] And my editors have heard me say this a thousand times – and I edit myself – but throughout “Cartel Land” and “City of Ghosts,” [I like to say] that context is a slippery slope. Too much context, people want to know more and then there’s this expectation that they’ll always be spoonfed what everything means and it takes away the drama. When you’re watching a [narrative] feature film, you’re often given bits of information at different times, not understanding [the whole story until the end]. But there is a certain amount of information that is necessary to care or to understand the journey of these guys, how they got started, the context in which the group was formed and [what happened] when ISIS came into town. That was all really important, but tough in the edit room to make that footage feel as alive as the verite footage that I shot. My guiding principle in the editing room, whether it be on the motorbike in the streets of Raqqa or in the room with Aziz as he’s shaking at the end, I want to make the audience feel like they are there.

A scene from Matthew Heineman's "City of Ghosts"There’s a particularly beautiful shot, which I assume came from a drone, as they’re fleeing Raqqa. How did you get that?

That shot I didn’t shoot myself. I was completely unable to go to Raqqa. I would’ve been killed, so that actually was shot, I believe, on the outskirts of Raqqa or right before ISIS took over. Most of the footage from Raqqa comes from the group itself. Again, no Western journalists were allowed into the city, so it’s either from the group [RBSS] themselves or it’s from ISIS. And we combed through hundreds and hundreds of hours of ISIS footage.

In general, like “Cartel Land,” this has a cinematic grandeur to it, but at the same time, you must’ve had to have been as inconspicuous as possible with the equipment. Was that a challenge?

Yeah, I don’t have a lot of people around. I feel like I’m operating at my best when I’m operating alone with no one else around, and I don’t rig out my camera. It’s a very small package of just the body, shotgun, wireless microphone and I like to be alone in the room with the guys I’m filming with to develop that rapport and become part of the fabric of their daily lives so eventually they don’t really notice that I’m there.

Artistically, one of the hardest things [about “City of Ghosts”] was that unlike “Cartel Land” where there’s a sort of visual feast everywhere you went and you’d just have to make all these choices between good options of where to go, who to follow, where to be, this film was very constrained. It was very much in closed quarters in these smoky safehouses for what mostly amounted, to some degree, to guys on cell phones and computers. So how to find the cinema – the drama – in that, and the humanity, was definitely one of the hardest artistic challenges.

You manage to bring out the cinema in it. One of the most harrowing moments in the film takes place in a hotel room when Mahmoud watches an ISIS-produced video of his father’s death – not for the first time. What were the circumstances around capturing that?

It happened quite organically. We were talking on camera about his father’s death and he said that he actually watches his father’s death because it gives him strength. When he said that, it felt like it would be okay to film him actually watching it because that’s something that he does, so I was able to capture that, which I felt very conflicted about while I was filming.

A scene from Matthew Heineman's "City of Ghosts"When you’ve got a moment of violence like that, is there an additional consideration while filming of what to capture so an audience won’t tune out completely?

That was a tightrope I was walking throughout the film, not just in that moment. And I shot [Mahmoud] watching that in a way, knowing that the “drama” was not in this crescendo moment of his father actually getting killed, which was so gruesome and awful and shot really horrifically seemingly with a Phantom camera in slow motion, really horrifically. I knew at the time I didn’t want to show that and I didn’t want to exploit that. But it really was his reaction to that and his interpretation.

Throughout the film, it was this tightrope of how much violence to show and as far as ISIS footage and footage from the guys themselves from within Syria, my guiding principle was I don’t want to shy away from the violence. I want people to feel the horror of what it would be like to walk out of your house and see that beheaded head on a stick or a crucified body in the streets. But at the same time, I didn’t want people running out of the theater, so that was a balancing act in the editing room for sure.

What’s it been like to travel with this?

It’s been really wonderful, especially at Sundance being with all the guys. And tragic too. Our last screening at Sundance was extraordinarily emotional. It was the day after the first Trump ban, immigration ban and to be on the stage with these guys who a lot of people consider heroes and who are at the very least allies in this fight against terrorism and against ISIS, because of the color of their skin, because of the country they were born in, they’re no longer welcome here. But for the most part, it’s been really wonderful to have audiences be able to see the film and then get to meet them afterwards.

“City of Ghosts” is now available on Amazon Prime.