Ready for my closeup Anwar Congo, right, prepares to re-enact one of the hundreds of murders he committed in 1965. (Courtesy of Drafthouse Films)

In the early hours of October 1, 1965, a group of junior officers in the Indonesian military assassinated six generals and threw their bodies down a well. Their coup attempt was crushed by nightfall, but the murders became the opening scene in the founding of present-day Indonesia. The senior surviving officer, General Suharto, accused Indonesia’s Communist Party of being behind the killings, and, in the words of historian John Roosa, an authority on these events, “orchestrated an extermination of persons affiliated with the party.” This was the height of the Cold War, and Indonesia had the largest communist party outside of a communist country, with affiliates ranging from labor unions to intellectuals to peasant farmers. In the name of saving Indonesia from the threat of Marxism, the army and its affiliated militias carried out one of the largest mass killings of the 20th century, executing 1.5 million suspected communists in less than a year.

By March 1966, Suharto was running a military dictatorship that would last more than 30 years, and the story of the murdered generals was the pretext for his entire regime. “Under Suharto,” Roosa explains, “anti-communism became the state religion, complete with sacred sites, rituals, and dates.” Each year, Indonesian students were required to view a graphically violent, Hollywood-style dramatization of the murders. The executioners, many of them active gangsters, were celebrated as national heroes and rewarded with political power. Even after the Suharto regime ended in 1998, this power structure remained. There was no official apology or reconciliation, and the killers continued to live alongside their victims’ families. The extermination of communists became as much a part of Indonesia’s founding mythos as the extermination of Native Americans is a part of America’s—a bit of necessary unpleasantness.

The Act of Killing, a global success on the film-festival circuit that had a brief theatrical run in the US this summer, tells the story of the massacre from the perspective of the men who perpetrated it. Joshua Oppenheimer, the film’s director, encouraged former executioners to re-enact their deeds any way they wished. He filmed the re-enactments and the creative process behind them, and blended the two into a documentary in which the killers serve as both subjects and artistic collaborators. The premise sounds offensive and deliberately provocative, like some outr√© work of post-colonial, art-house horror. But the idea emerged organically, over nearly a decade of filming in Indonesia, as a documentary and investigative technique well suited to tell the story of the massacre.

When Oppenheimer first arrived in Indonesia in 2001, he began talking to surviving victims and their families. He and his co-director, Christine Cynn, lived for a year with a village of survivors in North Sumatra, working on an experimental film that became the forerunner to The Act of Killing. Filming was constantly disrupted by local police or military or thugs, and they worried for their subjects’ safety.

The silence enforced on the victims’ families was particularly ironic when compared with the boastfulness of the killers themselves. And when Oppenheimer hit upon the idea of turning to these men for an explanation of the massacre, all obstruction ceased. He would simply ask a former executioner what he did for a living and, within minutes, be taken to a massacre sight and told horrific stories about beating people to death with bricks. In February 2004, an executioner took the film crew to a site near a river where he had helped kill 10,500 people in less than three months, then posed for pictures that look eerily like the ones that would emerge from Abu Ghraib just two months later, smiling and giving the thumbs up as the river into which he had dumped the bodies meandered through the background.

A common misconception among viewers is that Oppenheimer somehow tricked the killers and their associates into participating in the film—that he told them he was making a film that would celebrate them, or that he wanted to make them stars in an action movie. This misconception is based on the perfectly logical notion that anyone who had taken part in such an atrocity would understand the danger of admitting to war crimes on camera. But these men had never been accused of anything; they were heroes. And while Oppenheimer sometimes had to hide his disgust at the casualness, or even joy, with which the men relived their deeds, he never had to be anything but honest about his intention to make a film that highlighted their role as mass murderers.

Michael Meyer is a CJR staff writer. Follow him on Twitter at @mcm_nm.