If the truth hurts, then the new Ken Burns documentary The Vietnam War is a kick in the stomach.

Burns and his co-director Lynn Novick spent 10 years making the 18-hour-long series The Vietnam War, resulting in an extensive report on the decades-long conflict. Across 10 episodes, Burns and Novick’s lens focuses on our country’s mistakes and the horrors of modern warfare. Burns describes the work as “emotional archaeology,” and plenty of emotions are dug up throughout series: from the participants in the film, its viewers and even the filmmakers themselves.

“This film was exponentially more difficult and more challenging intellectually, emotionally, creatively, organizationally — just everything about it,” Novick said during an interview with both filmmakers at KQED last week. “We’re not really the same people we were 10 years ago.”

The Vietnam War, which premieres on PBS in September, portrays the American government as missing the bigger picture, fatally focused on the spread of communism rather than the country’s desire for independence. The filmmakers establish this narrative in the first episode, which oscillates between France’s struggle to keep its hold on Vietnam and bloody scenes of America’s war in the same country a decade later. From the get-go, the documentary becomes frustrating for the viewer, who knows what’s going to happen but can’t do anything to stop it.

“It’s like a horror film where you see the teenager in her nightgown hearing a noise and coming out of a room, and you’re going, ‘Stay in your room. Don’t walk over there. Don’t go into the bathroom,’” Burns said.

Burns and Novick interviewed 80 sources for the film on a subject that scarred many, both physically or emotionally. Novick said that the reporting took a personal emotional toll, as she and Burns heard dozens of devastating stories and pored over thousands of images and hours of footage from a war that resulted in millions of civilians being killed, many of them women and children.

“When we’re looking at a piece of footage or a still photograph, it’s real to us. You hear the sounds, you see a child screaming — that sort of gets under your skin,” Novick said. “It’s almost hard to find words to explain how you’ve changed from just being exposed to this material, let alone trying to organize and make sense out of it.”

But the filmmakers were on a mission. Assisting them was the fact that enough time had passed since the conflict, and many who were affected by it at home and abroad were ready to tell their stories. They also made a concerted effort to speak with Vietnamese people on both sides of the conflict — North and South — ensuring for a more comprehensive viewpoint and moving away from most other American-centered documentaries on the war.

“What we need, not just in our understanding of Vietnam, but what we need right now in our understanding of ourselves, is an ability to tolerate a view that that isn’t quite our own — that’s just even a couple degrees different,” Burns said.

Indeed, statements from North Vietnamese soldiers prove to be the most poignant. While discussing how Americans reacted to their fellow soldiers, Viet Cong veteran Le Cong Huan notes that they “cried and held each other. When one was killed, the others stuck together.”

Added Cong Huan, “Americans, like Vietnamese, have a profound sense of humanity.'”

That humanization in the film extends to all parties involved in the war. For example, Burns and Novick said that they “obsessed” over the use of the term Viet Cong to describe the North Vietnamese army, who called themselves the National Liberation Front. Viet Cong has its origins as a derogatory term meaning “Communist Traitors to Vietnam.” (They ended up using the term in the film, but not the accompanying book.)

These past few weeks, Burns and Novick have been touring the film, showing it across the nation to critical acclaim — some publications are calling The Vietnam War their best work yet. Novick has even expressed concern that she and Burns would never work on a project “this important ever again.” (Burns insists that they will.)

For now, the two are enjoying the fruits of their labor, witnessing the overwhelming impact it has an audiences all over the nation.

“The first time we watched the whole film in one fell swoop — over four days — with some of the people who are in it, no one could talk when it was done. People were sobbing. I was sobbing so much I had to leave the room,” Novick said.

“In that moment we were overcome with the fact that we had relived the war with a group of people, some of whom had been in it,” Burns said. “It was the opposite of trauma — it was catharsis.”

‘The Vietnam War,’ a new 10-part, 18-hour documentary film series directed by Ken Burns and Lynn Novick, premieres Sept. 17, 2017, on PBS stations nationwide. Check your local listings for times.