A chilling black-and-white photograph freezes Lt. Col. Felix Sparks in time.

Bodies slumped against a wall, weapons still hot, smoking. Sparks’ pistol raised overhead, his other hand, palm open, signaling to stop the spontaneous execution.

His own troops were enraged as they arrived at Dachau concentration camp to find piles of dead naked bodies in train cars and dying prisoners behind barbed wire.

Those same men, the Army’s 157th Infantry Regiment, part of the 45th Infantry Division, had borne the war on their backs from Sicily to the heart of Germany during more than 500 days of combat in less than two years.

Sparks, and the regiment’s companies under his command, are now the focus of a four-part animated series released on Veterans Day on Netflix, “The Liberator.”

The series, at times heart-pounding, other times full of a profound stillness, presents timeless slices of the combat experience — fear, chaos, confusion, bravery, despair, callousness, tenderness and camaraderie.

But it also brings forth issues of racism, the challenge of leadership and the internal battle to retain one’s humanity in the face of utter savagery.

But long before it was a Netflix series, it was a book by the same name. And it was that photograph that caught author Alex Kershaw’s eye, the catalyst for years of research to set down the tale.

“The Liberator,” by Alex Kershaw, is the book on which the four-part Netflix series of the same name is based. (Alex Kershaw)

An already accomplished author of six books chronicling World War II, Kershaw was looking for his next story when he stumbled upon that frozen moment. Next, it was a friendship with a veteran of the 45th ID that drew him into the research. Finally, a fortunate trip allowed him to interview Sparks only months before his death in 2007.

Countless hours of research and interview after interview peeled back more layers of not only Sparks’ journey, but the men who served alongside him.

The 157th Infantry Regiment — and their respective division — were the most diverse set of soldiers the war had seen. Drawn from more than 50 Native American tribes and Mexican-American recruits, some who couldn’t speak English, the unit would see more fighting than almost any other in the war.

By the end of the conflict the 157th IR would accrue nine Medals of Honor, 61 Distinguished Service Crosses, 1,848 Silver Star Medals, 38 Legion of Merit Medals and 59 Soldier’s Medals. Sparks would receive the Silver Star Medal for valor in combat.

Of them, Gen. George S. Patton would say they were “One of the best, if not the best division in the history of American arms.”

Army Times spoke with Kershaw on the eve of the series release.

Editor’s note: The following has been edited for clarity and length.

Q: You’ve written at least nine books to date on World War II. What is it about the conflict and the stories that continues to bring you back?

A: In the 70s when I was young we had only two or three channels on TV. There was always a movie on Sunday nights. “The Great Escape,” “The Dam Busters,” “Battle of Britain.” I remember Veterans Day, or Remembrance Day in England was always a huge deal. They’d show it on the news, all these rows and rows of World War I veterans, and my dad would tell me about them because my grandfather had served in the trenches.

My mother’s father died in the British Navy in World War II. So, she never really had a father. That stays in the family. You’re aware of what it cost. Then I became a journalist after college, but in college I studied history and we read everything but World War II. As a journalist I eventually went down and did a story about the Channel Islands, one of the only British lands occupied by the Germans during the war. Now, after 20 years of writing about it, it gets into your blood.

Q: You met Sparks during this process. Could you tell us more about him and what you learned in researching the story?

A: First I found the photo and learned some of the story, then I called up the 157th Infantry Regiment Association and met Jack Hallowell. I started talking with him, but still couldn’t work out a way to tell the story. So, I left it alone for a year or two.

Jack called me later and said Sparks was dying, so I went out to Colorado to interview him on his deathbed — he died later that spring. He was a very outspoken guy. The proudest point in his life was being a company commander. He memorized all the names of his more than 200 soldiers, their wives, children, where they were from. But he wasn’t overly familiar. He was a hard ass and a stickler for discipline. But every guy who put his life on the line for him knew he was going to look after them. He led from the front, business all the time. He was very, very smart and very calm under pressure.

The universal fear in World War II for officers — and I think it’s still very common — was how they were going to perform. Sparks was surprised when he could keep it together when things got really hard. He didn’t like people abusing their power. I’m still fascinated by him telling Maj. Gen. Robert Frederick, the division commander, “You just got my entire company killed. You made a decision and my guys paid for it.” But he did it. I think his men respected him because he was prepared to stand up.

Q: The 45th ID, and specifically the 157th IR, were very racially diverse units for their time. How did Sparks handle the additional burdens his soldiers faced both at home and abroad?

A: He’d grown up in a region where he knew the discrimination that Mexican-Americans and Native Americans had faced. He didn’t worry about their own abilities but he did wonder, would they fight for Uncle Sam when Uncle Sam’s done nothing for them? But from the beginning they fought as excellent soldiers.

Q: What did you learn from Sparks and your research about the incident at Dachau?

A: Some of his guys went crazy. A lot of them were very keen on handing out some kind of vengeance. They went through the complex and kicked out anyone in an SS uniform. But most of the actual camp guards had fled. The remaining SS were frontline soldiers recovering from wounds and hadn’t been involved in the camp.

Sparks had left Lt. Bill Walsh in command of soldiers in the coal yard while he went to inspect the rest of the camp. They didn’t know what they were seeing. Walsh ordered the guys to start firing. Sparks rushed back and ordered the guys to stop. He kicked the machine gunner and shoved him off the gun and said, “There will be no firing unless I give the order.”

Years later he said it was something people couldn’t get their head around, something beyond what people could process. They’d seen all sorts of horrific things, but that was very disturbing on a profound level. Those memories of what human beings did to other human beings and how depraved and dark humanity could be … for the rest of his life he was very outspoken about Holocaust denial and would get very angry if anybody questioned if it ever happened.

Q: What do you think of the Netflix series?

A: It was amazing. I cried my eyes out and laughed very hard. They did a really, really fantastic job. It’s entertaining, informative and extraordinarily accurate. The irony is that before this if somebody told me they would turn one of my books into an animated TV series, I would have thought it was an odd choice. Then again, I became absolutely obsessed with World War II when I was nine or 10 years old and found a stash of comics about the war in my grandparents’ house. I just devoured them. I remember my mom saying she saw me walking along a street and worried I’d run into a street sign because I had my head buried in these comics.

Q: Do you think that the series might appeal to people who might not normally look for books on World War II?

A: I hope and pray that’s the case. The idea that a teenager or anybody from 16 into their 20s wouldn’t be interested in these stories would be insane, because these stories are about them.

I’m a blatant booster for anything that gets people into history. And if this does, that would be amazing. If you’re a young American and you don’t know about World War II, what was sacrificed, what was earned, and understand what it really came down to, then you can’t know what it means to be an American.

The show is trending really high in Italy now, where much of it took place. It’s just fantastic to think of a 15-year-old in Italy learning about what happened there and who liberated their country. There are plenty of young people who didn’t grow up with “Band of Brothers” or “Saving Private Ryan.” It’s a different generation now. But with this they can really learn what America did at its best.

Originally published on Military Times, our sister publication.