Holocaust survivor Leon Schwarzbaum, a key witness in trials of alleged Nazi war criminals, died March 13 at the age of 101, according to the International Auschwitz Committee (IAC). “His death represents a great loss to the collective memory,” said Christoph Heubner, executive vice president of the committee.

Mr. Schwarzbaum testified in 2016 against former Auschwitz camp guard Reinhold Hanning, who was sentenced to five years in prison. In late 2021, he appeared as a witness in the trial of Josef Schuetz, a former guard at the Sachsenhausen camp, and had been scheduled to testify again.

Mr. Schwarzbaum was the only member of his family to survive the camps of Auschwitz, Buchenwald. After the war, he campaigned tirelessly to keep the memory of the Holocaust alive through lectures and talks around the world. He had often expressed anger and regret that so few Nazi war criminals had been brought to justice. “He did not want hatred, he wanted justice,” the IAC said.