On December 20, 2005, the man known as the “conscience of the Holocaust” passed away in Vienna. Simon Wiesenthal was 96 at the time of his death, and spent even those last days working to bring Nazi criminals to justice. He was a self-appointed defender of millions of victims, building a legacy that placed him among the most revered Jewish leaders in the world.

Born Szymon Wiesenthal on December 31, 1908, in what is now western Ukraine, the man who would become a legend grew up in near-impoverished surroundings. Wiesenthal’s father sold sugar and earned a modestly successful living, but the family struggled for survival amid rising political clashes between Soviet, Ukrainian and Polish forces.

Despite adversity, Wiesenthal studied to become an architect before the outbreak of war demanded an end to his profession. He married his high school sweetheart Cyla, and the pair was deported to the Janowska Street camp in 1941. Eventually, Wiesenthal was able to help his wife flee, trading on her blond hair to pass the young woman off as a Polish Christian.

Wiesenthal escaped himself in 1943, working briefly for the Polish Underground. He was recaptured in 1944 and sent to the Gross-Rosen camp, then forced to participate in two separate death marches: first to Chemnitz, then to Mauthausen.

It was at Mauthausen that Wiesenthal finally greeted liberation. He had been hospitalized for three months due to an amputated toe and case of gangrene caused by the death marches. When American troops entered the camp, the 6-foot-tall Wiesenthal weighed 99 pounds.

The years following Hitler’s regime saw immense change in the way Europe targeted and prosecuted war criminals. Much of that transition is credited to Wiesenthal’s tireless efforts. Reunited with his wife, Wiesenthal set out on a path to locate Nazi officers, many of whom had gone into hiding and assumed new identities.

Through his work, Wiesenthal famously helped track down Adolf Eichmann, one of the Holocaust’s most prolific killers. The global community had previously thought Eichmann to be dead, and his recovery led to a notorious trial in Israel and an eventual hanging in 1962. For decades to come, Wiesenthal would call it one of his greatest successes in life.

In total, Wiesenthal is ascribed with bringing 1,100 Nazis to justice, including the man responsible for Anne Frank’s deportation. He worked with Sen. Robert F. Kennedy to end a statute of limitations in Germany that would have meant Nazi criminals could not be prosecuted after a certain length of time. He also brought to light the story of Raoul Wallenberg, who is known today as a hero for his work smuggling thousands of Jews out of Hungary. Wiesenthal collected documents, transcribed witness accounts, and flew across the globe to ensure a collective account of Holocaust atrocities survived.

“I considered that my self-appointed task was holy, and my determination became the more pronounced, the more I learned how Jews had been abused,” he wrote in his memoir, “I Hunted Eichmann.”

Wiesenthal’s crusade made him incredibly unpopular for years after the war, among both non-Jews and Jews alike. Some saw his actions as an effort to dig up buried wounds during a time when many wanted to forget altogether. Martin Mendelsohn, a DC lawyer who helped set up the US’s Nazi-hunting Office of Special Investigations, said Wiesenthal “kept the memory of the Holocaust alive when everyone wanted it to go away. When Jewish groups wanted it to go away, he wanted to keep it alive.”

It would be decades before Wiesenthal enjoyed any level of thanks for his work, but thanks he did eventually receive. He was honored in the US with both a Congressional Gold Medal and the Presidential Medal of Freedom, and in the UK with an honorary knighthood. He has been decorated in Israel, Germany, Austria, France, the Netherlands, Luxembourg and Poland.

In 1977, when a Jewish human rights group was set up in California, it was named in Wiesenthal’s honor. With that action, his name became one of the most recognizable on Earth. Today, the Simon Wiesenthal Center is a global advocate and a preeminent Holocaust trust, a testament to the memory of a man who would not let the world forget. Now, with Holocaust education a prominent part of the collective culture, it may seem unfathomable that the Jewish community was ever in danger of losing these records. It is due in no small part to Simon Wiesenthal that we remember.

“I’m doing this because I have to do it,” he once said. “I am not motivated by a sense of revenge…Even before I had time to really think things through, I realized we must not forget. If all of us forgot, the same thing might happen again, in 20 or 50 or 100 years.”

Famous quotes from Simon Wiesenthal:

“Humor is the weapon of unarmed people: it helps people who are oppressed to smile at the situation that pains them.”

“Survival is a privilege which entails obligations. I am forever asking myself what I can do for those who have not survived.”

“When history looks back, I want people to know that the Nazis could not kill millions of people with impunity.”

“When we come to the other world and meet the millions of Jews who died in the camps and they ask us, ‘What have you done?’… I will say, ‘I didn’t forget you.'”

“Justice for crimes against humanity must have no limitations.”

“Violence is like a weed–it does not die even in the greatest drought.”