As part of the research for his new documentary, “Auschwitz: Inside the Nazi State,” filmmaker Laurence Rees visited “a very brave Ukrainian national, someone who fought both the Red army and the Nazis and was subsequently sent to a gulag.

“We were doing the interview over a cup of tea when he says, ‘By the way, I’ve been meaning to ask, what do you think of the international Jewish conspiracy?'”

Rees is on the phone from his office in London, promoting his six-hour film and the accompanying book. But even across the Atlantic, the tone of his voice clearly indicates his incredulity at the comments. It was not the only time he was stunned by things people said, remarks that invariably provoked in him disbelief coupled with a sense of despair.

There was an interview with a guard who smiled fondly and unapologetically as he recalled shooting women and children. Another says Jews cheated his family. The interviewer responds, “But those weren’t the same Jews you killed.” The guard’s reply: “They’re all Jews.”

“Auschwitz” airs on PBS from 9 to 11 p.m. on three consecutive Wednesdays starting Jan. 19. The book, with the same name, was just released by Public Affairs Press.

Rees, who turns 48 on the day of the show’s premiere, is not Jewish. His interest in World War II is based on familial ties. During the war, his father attended the Royal Air Force’s navigator’s school in South Africa. He finished first in his class and was assigned to the school to train other navigators.

“Every other member of his class was sent to Europe or the Pacific to fight and was killed,” Rees said. His father never saw action, though he was injured in a plane crash. An uncle in the merchant marine was killed when submarines attacked his Atlantic convoy.

“The Second World War was alive in my family,” he said. “It was the subject I was most interested in in school. The Second World War, at least when I was growing up, was the only way to understand the world situation. A whole range of things makes sense” if you understand World War II, he said.

But time passes and things change. “My daughter thinks of World War II as the Battle of Hastings, as history in a way it wasn’t for me.”

There was very little opposition to the project, and, ironically, Rees notes, what there was came from Jews who essentially said enough already. But Rees disagreed. There was a lot of new material uncovered in the archives of the former Soviet Union.

Before he began work on the documentary, the BBC commissioned a study on Britain’s knowledge of Auschwitz. Four thousand people were surveyed, and the results were eye-opening.

“It came out that nearly 50 percent of the British population didn’t know what the word ‘Auschwitz’ meant. And that rises to 60 percent of women under 35,” the filmmaker said.

Rees’ research revealed Auschwitz originally housed Russian POWs. It was only later, as Hitler’s Final Solution moved into high gear that Auschwitz was expanded.

Rees is creative director of history programs for the BBC. He is also a writer and independent producer whose award-winning documentaries have been shown around the world. Among them: “The Nazis: A Warning From History” (1997), “War of the Century” (1999) and “Horror in the East” (2000), the last about the war in the Pacific.

“Auschwitz” is not just about the camp, but the decision-making process surrounding the Final Solution. Rees said the process, which took three years, was “very depressing. But most depressing was that roughly 6,500 people in the SS worked at Auschwitz and survived the war. Only about 10 percent were tried. Ninety percent weren’t even prosecuted.”

Moreover, he adds, “I don’t believe that the mentality behind this, the mentality that wants to create scapegoats, has changed. It may not be directed necessarily at Jews, but it’s still there.”