For his recent documentary on Cambodia, Angkor Awakens, American filmmaker Robert Lieberman interviewed more than 140 individuals. Dozens made it onto the screen.

The result is an ambitious study of Cambodian politics as it operates within the collective psyche, spread across generations. But the film is aimed primarily at a Western audience, the director says.

Lieberman himself is a character. A physicist who teaches at Cornell University in the US, he’s written several novels and made a handful of films, including the documentary They Call It Myanmar, which drew global praise when it was released in 2012.

“This was a much more complex story,” he says via Skype this week. “Cambodia has a tangled history.”

Angkor Awakens was four years in the making. It arose from a personal interest in the generational effects of genocide – Lieberman is a child of the Holocaust – and it shines in its exploration of inherited trauma, and the dangers of keeping silent.

Lieberman spent four years travelling back and forth to Cambodia to film. Photo supplied

In an early scene, the director interviews Kenny, a 12-year-old boy, as he sits on a couch with his mother. He stoically recounts the death of his grandmother and uncle – the latter for stealing a fish head to eat. But when asked if his mother’s experience affects him, the boy collapses in sobs.

“I think it’s right to tell,” his mother says. “But I don’t want to pass on what I’ve been through.”

It’s a feeling with scientific basis, Lieberman explains. “Studies show that when mothers have experienced extreme trauma, there are these methylated groups that appear attached to the DNA, and they affect the expression of genes,” he says. “This stuff ripples through the generations. My psychological bags are always packed.”

A psychiatrist and other children of war in the film call it baksbat, or broken courage. Most Cambodians wouldn’t self-diagnose with PTSD, but quite a few claim baksbat – it is scattered throughout Lieberman’s interviews.

At its core, Angkor Awakens is focused on Cambodia’s youth. Photo supplied

Survivors speak of living for today, not tomorrow. Others express guilt for escaping when they still could. Three young people tell Lieberman that their parents often offer up a similar warning: “If the Khmer Rouge come back, you will die.”

The film takes on the saga of Cambodia’s history for those beyond its borders with the voice of former US ambassador John Gunther Dean, who fled Cambodia in 1975 and shares Lieberman’s Holocaust heritage, as well as some familiar Cambodian history buffs.

Key moments – Sihanouk’s overthrow, American carpet bombings, the takeover of Phnom Penh – are cleverly narrated with customised sbek thom puppets, a device Lieberman credits to producer Deborah Hoard. It doesn’t trivialise the violence.

The film takes a hard line on the United States’ clandestine bombing of what Cambodia – and its effects on the rise of the Khmer Rouge – by letting history and the experts speak for themselves.

At this point, Prime Minister Hun Sen appears on screen. “There are two reasons for me to join the Khmer Rouge,” he says. “I love King Sihanouk . . . and I have seen with my own eyes the aggressive bombing by American armed forces and the South Vietnamese. The second point is important to me.”

With the aid of the former US ambassador, Lieberman was able to secure an interview for the film with Hun Sen in New York. (The director already had some political star power: conversations with Sam Rainsy and Tioulong Saumura, and Son Soubert.)

Lieberman had pre-written questions, but they scrapped them. What followed was a two-hour conversation that ranged from personal life to land disputes. “In itself, it’s a historical document,” he says.

The footage is used sparingly – only a few minutes in total – and at critical junctures. Later, when some express fear of political instability if the ruling party falls, the prime minister poses a similar question, in the third person: “What is the post-Hun Sen era?”

Lieberman provides few answers, but he does engage with the root of this uncertainty: baksbat. “If Hun Sen were overthrown, what does that mean for the country? Does it mean instability? Or does it mean a move towards democracy?” he asks. “I don’t know.”

For all its exploration of the darkness, Angkor Awakens is not a tragic film, and Lieberman is the first to say this. He did, after all, change the title from Breaking Baksbat. (“It didn’t reflect the film,” he says.) In the end, he returns to the young generation, as he did in They Call It Myanmar.

The film uses traditional shadow puppets to recreate violent action. Photo supplied

Lieberman captures young people engaged in the arts, and in politics – a call back to the “golden age” he dwells on earlier in the film. The director conducted interviews on the fly during the 2013-2014 demonstrations, and captures their energy onscreen, though without much context.

The note of optimism could strike a sour contrast for those following Cambodian politics day-to-day. But Lieberman says he has aimed for something timeless.

“We will show it in Cambodia. The question is just censors,” Lieberman says with a laugh. “But Hun Sen and I are now friends.”

Angkor Awakens: A Portrait of Cambodia will soon screen in the US and Europe, with hopes for a Cambodian premiere. For more information: angkorawakens.com.