The complex international war in Bosnia and Herzegovina between Serbs, Croats and Muslims ignited by the breakup of the former Yugoslavia, resulted in some 100,000 dead. When fighting broke out in Sarajevo in 1992, Bosnian Serb military chief Ratko Mladic responded by unleashing a campaign of terror against the multi-ethnic population there, massacring thousands of civilians in a multiyear siege. In the Srebrenica massacre in 1995 alone, more than 7,000 Muslim men and boys were killed in what was supposed to be a United Nations safe zone.

In 1995, Mladic was indicted by the UN-established International Criminal Tribunal for the former Yugoslavia for war crimes and atrocities but went into hiding. He was finally arrested in Serbia and put on trial in 2012 for genocide and crimes against humanity. In 2017, he was convicted and sentenced to life in prison. In The Trial of Ratko Mladic, premiering March 19 at 9pm, Frontline filmmakers Henry Singer and Rob Miller chronicle the five-year war crimes trial of Mladic, known as the Butcher of Bosnia.

One of Britain’s most critically acclaimed documentary directors, Singer has won or been nominated for every major British documentary award, and his films have been screened at festivals around the world. Miller began his career working for a human rights organization before crossing over into filmmaking. He has more than 15 years of experience producing documentaries, collaborating with Singer on a series of films, including Last Orders, On a Cold Friday in November and The Betrayed Girls.

In The Trial of Ratko Mladic, the filmmakers team up to offer unprecedented access to prosecution lawyers and hundreds of witnesses who testified about the horrors they experienced firsthand. Hear the heart-wrenching stories from families whose loved ones were taken prisoner during the war and were never heard from again.

“Seeing extraordinary pain and terrible trauma like this was really a reminder that this isn’t just history—these are people who experienced terrible things then,” said Miller, who covered Mladic’s trial from the beginning. “For them, the war has never really ended.”

The documentary also includes excerpts from Mladic’s defense lawyers and his supporters so viewers can understand the conflict from all sides. By showing both the prosecution and the defense, Miller said he wanted to present a story that is fair. “We’re hoping that there is value in trying to understand those narratives,” he said.

Although the trial exposed the worst of humanity, there is still a glimmer of light that shines through—that so many witnesses came forward to participate in the process and describe in their own words what they endured so that the truth of what happened could be established. It’s a very human film, Miller said, highlighting the resilience of people even when they are put in the worst of situations.

This is a film that transcends Bosnia. “I think there are lessons that can be learned from this tribunal and this period of history which are really important to the world that we live in now, where the politics of division seems to be very much on the agenda and very much the lingua franca of the day.”

The Trial of Ratko Mladic airs on Tuesday, March 19 at 9pm on WGBH. Watch a preview below.