Rob Cohen filming at the Buchenwald crematorium.

For Rob Cohen, the road to Buchenwald started at Paramus High School.

It was a high school English teacher who saw the hint of an interest in filmmaking in Mr. Cohen. “He encouraged me, made it possible for me to make a couple of small films with a Super Eight camera,” he said. His interest sparked, he crafted a film major at Yale, which was not yet formally offering one when he graduated in 1974.

A few years ago, Mr. Cohen, who now lives in New York, created two future-focused documentaries for CBS and the Discovery Channel: FutureCar and NextWorld.

But his project opening in two New Jersey theaters this week looks backward. “Kinderblock 66: Return to Buchenwald” tells the story of four boys who survived Buchenwald, and chronicles their return visit there in 2010, on the 65th anniversary of their liberation.

Mr. Cohen wrote the documentary, but the lead force behind it was Steven Moscovic, a friend whose father was one of those boys. The two had become friendly as colleagues, so when Mr. Moscovic decided to make a documentary about his father’s experience, he brought Mr. Cohen on board.

“It looked like an extraordinary gift a son was giving a father,” Mr. Cohen said. “I wish I could do something like that for my dad.”

In 1945, Steven’s father, Alex, was 13 years old. Born in Sobrance, which had alternately belonged to Hungary and Slovakia, he had been in Auschwitz-Birkenau in Poland, and then, as the Germans retreated on the eastern front, he was shipped by train to Buchenwald in Germany, enduring nine January days in an open coal car.

Day-to-day control of Buchenwald was in the hands of a Communist-led underground, whose international connections made them useful to the SS officers who ruled over them. The man in charge of the barracks where Alex Moscovic and his brother were assigned told them there was a better place they could go to, Alex Moscovic said last week. “He said that they have a barrack, number 66, that only had children. He suggested that it would be much better for us to be with other boys. He made the arrangements, and a few days later we were transferred. That’s when we met Antonin Kalina.”

Mr. Kalina was a Czech Communist who had been imprisoned in Buchenwald since 1939. He oversaw a barracks that was designated for the children who were arriving from the East. Located in the most remote part of the camp in an area rife with disease, it was far from the eyes of the SS. He did everything he could to save the children in his care. He exempted them from labor obligations and twice-daily roll call. And when, on the eve of liberation, the SS wanted to gather the inmates for a final death march, Mr. Kalina changed the boys’ badges to read Christian – and told the SS that there were no Jews in the barracks.

More than 900 Jewish boys survived this way, among them Elie Wiesel and another Nobel laureate, Hungarian novelist Imre KertÃ©sz.

Mr. Kalina returned to Prague after the war, and died with little recognition. Last December, he was honored by Yad Vashem as a righteous among the nations, following entreaties by the Moscovics.

“He deserves it,” Mr. Moscovic said. “I don’t have too many heroes, but he’s one of my heroes.”

Mr. Cohen found the story Mr. Moscovic and the three other survivors told amazing for what it said about human resilience.

“Sixteen hundred of these boys were crammed into a barrack, formerly a house barn, a tiny little space that shouldn’t have accommodated more than 40 people,” Mr. Cohen said. “They were from all these different countries. They were Hungarian and Czech and Polish and Lithuanian, and they fought like teenage boys do. They were crammed up check by jowl.

“The people who ran the barrack make sure they had classes for these kids. They taught them Jewish history, they taught them math. Life was happening even in this unbelievable pressure cooker.

“Not all of their life had been sapped from their spirits.”

For Alex Moscovic, the hardest part of the film “was basically to go back to Buchenwald, and seeing it. Though Buchenwald by the time we went back there didn’t look like the original Buchenwald. All the barracks were destroyed while the East Germans were in control. The rest of it is still there: the barbed wire, the main building the SS had, one other building. But barrack number 66 no longer exists.”

As a filmmaker, Mr. Cohen found shooting in Buchenwald “a thrill. It created an enormous visual opportunity to make interesting abstract pictures.”

Mr. Cohen said Buchenwald felt like the Holocaust memorial in Berlin.

“None of the barracks exist but there are these fabulous low-to-the-ground outlines of where they were,” he said. “You’re walking among the ghosts of all these buildings. This entire, huge, acres and acres of space is surrounded on four corners by guard towers and completely surrounded by barbed wires.

“It’s extraordinary. It’s a visual statement. It’s a landmark as opposed to a preserved historical artifact.”

After the war, at 15, the senior Mr. Moscovic came to the Bronx. Excited by the new technology of television, he studied at the RCA Institute and had 30-year career as a film editor at ABC Sports before retiring to Florida.

He was more than just a subject of Kinderbloc 66.

“Because my son was also the executive producer, I had a lot of input,” he said. “I said we should concentrate on the positive side, on what has become of the boys who were in barracks 66. So there are a few parts of when the Americans arrived and the atrocities, after that the film is basically concentrating on the four of us, on the type of life we led.

“Immediately after the war, some of the boys ended up going to Paris. There was a psychiatrist who took care of a hundred of the boys. She was a young woman and had just finished school; psychologically she was not ready for that kind of job. She wrote that by us going through the Holocaust we would never be normal again. She thought we would never be able to have children because of what we went through.

“I felt that we can show that four of us out of 900 were able to overcome what happened in the camps. We had normal families. We had children, we have grandchildren,” he said. (Steven the filmmaker is one of Mr. Moscovic’s two sons; he has six grandchildren.)

“All of our lives turned out pretty good,” Mr. Moscovic said. “The memories are still there but we are able to live a normal life. That’s the big difference in this documentary.”

Mr. Cohen agrees that this was the approach to take with the film.

“I think the film is wonderfully optimistic,” he said. “The four men and who they are and what they’ve done with their lives, the lack of hate that’s in their lives, it’s very uplifting. People came through this. These men came through this.

“Did they get robbed of their childhoods? I guess they did, on some very obvious level, maybe most levels. But they’re full human beings, fully generous, certainly generous in letting us make this film about their lives and they were very sharing.

“The film is very much in the present as well as in the past.”

One present-day touch that Mr. Cohen is proud of: He gave the four survivors mini’ature video cameras. “That’s a marvelous thing, seeing 80-year-old men being taught to use and embrace this modern technology. It serves as a real basis for a lot of the material in the film. A lot of the filming is done when they’re sitting by themselves. They’re kind of narrating their lives into it. It was just them and their stories and their secrets and their thoughts. It’s the most personal kind of testimony,” he said.

Since retiring, Alex Moscovic has told his story hundreds of times, speaking at local schools.

“It’s a subject that has to be told,” he said. “The more people who know about what happened in Europe during the Second World War, the better off we are. Hopefully because of that in the future they’ll do something about it, and we won’t have anything like that repeat again.”

Mr. Moscovic didn’t know how eighth graders would react to the film the first time he showed it at a school near his home in Hobe Sound, roughly a hundred miles north of Miami. The presentation was for the entire grade – about 300 students.

“Would these boys and girls be able to sit through a Holocaust documentary for an hour and a half?” he wondered.

“I introduced the documentary, and then went in back of the group and sat down to see what their reaction was.

“There’s no talking. It’s quiet. Now we are into about 10 minutes. It’s still quiet. Every once in a while I hear one of the girls sob. Then from another part of the group, I heard some more sobbing. And so on. We went through the hour and a half documentary until the credits came on.

“I start to answer the questions – the questions kept coming and coming. The next thing I know the bell sounds, the students have to leave their classes and go to their buses.

“The teachers said they had never seen anything like this before, a class of eighth”“graders sitting through a film of an hour and a half, and then another hour and a half of questions and answers. I came home and called up Steven. I said, ‘If we can keep the attention of eighth”“graders for this period of time, I think we have a winner.'”

How to watch

“Kinderbloc 66: Return to Buchenwald” will be screened starting Sunday, April 27, at the Digiplex Sparta Theater in Sparta and Digiplex Cranford in Cranford.

You can rent or buy a digital copy, or order a DVD, at http://bit.ly/kinderblock