Leo Pinter/HBO

For many who witnessed and survived the horrors of Nazi concentration camps, complete liberation did not come with the Allies’ victory in World War II. The shackles of post-traumatic stress and survivors’ guilt weighed on them for the remainder of their lives. For Harry Haft, escaping the Holocaust came at an unimaginable price.

Interned in the infamous camps at Auschwitz, Haft was forced to fight his fellow prisoners in win-or-die gladiatorial boxing matches for the entertainment of Nazi SS officers. Haft fought more than 70 times, his athletic build and skill allowing him to live another day at the cost of another innocent man’s life.

Haft told his story to his son, Alan, who published the book Harry Haft: Survivor of Auschwitz, Challenger of Rocky Marciano in 2006. From that account comes Oscar-winning director Barry Levinson’s film The Survivor (Wednesday, April 27, at 8pm ET/PT), a harrowing dramatization of one man’s perseverance through an unthinkable situation. Haft’s journey toward peace and reconciliation leads him to America, where he pursues a prizefighting career and a shot at the great Rocky Marciano.

“I did not know the Harry Haft story,” Levinson says. “I didn’t know a lot of the particulars until really getting involved in [the film]. We went to Auschwitz to walk around and see what was there, and spoke to some people who gave us information that we actually did not know. Some of the kind of insights to what might take place just in daily living in that regard, so that we can create as much authenticity.”

Star Ben Foster knew taking on the role of Haft would require deep mental, emotional and physical commitment. In addition to losing 60 pounds and spending time at Auschwitz, he completely immersed himself in research. “The Shoah Foundation guided us quite a bit,” Foster says. “I watched thousands of hours of Holocaust survivor interviews, spending time with Yiddish experts, learning about this world, the responsibility to honor survivors. And there aren’t many left who are still on the planet, those who have survived the camps. Some of their children are still with us. The immense responsibility to represent the complicated nature of this kind of trauma. I just had to not let the fear take hold and get lost in it.”

Joining Foster in the stellar cast are Vicky Krieps, Billy Magnussen, Peter Sarsgaard, Saro Emirze, Dar Zuzovsky, Danny DeVito and John Leguizamo.