This past Saturday, April 11, 2015, marked the 70th anniversary of the liberation of the Buchenwald concentration camp by the US army. Fittingly, this year the anniversary fell on the last day of Passover, giving a special meaning to the idea of coming out of slavery and into freedom. Five years ago to the day, I was in Buchenwald and the nearby town of Weimar filming a documentary about the efforts to save over 900 children and youth within the camp. The film, Kinderblock 66: Return to Buchenwald, followed four survivors who were liberated as young boys and told the story of their rescuer, Antonin Kalina, the block elder of the children’s barrack, block 66. This year, about 100 survivors, some well into their eighties, came back to Buchenwald again to remember, perhaps for one last time.

Among the returnees included all four of the survivors featured in Kinderblock 66 – Naftali Furst and Israel Lazar from Israel, Pavel Kohn from the Czech Republic and Alex Moskovic from the United States. This was the first time that all four were together since we filmed them five years ago and everyone was pleased and more than a little relieved that they were still able to make the journey back to the camp from which they were liberated so many years ago. Naftali Furst, 82, came to Weimar with his partner, Tova Wagman Siegel, and was also met by a group of 10 Austrian and German friends who had traveled up to seven hours to see him.“Naftali is the only survivor with his own groupies,” Wagman Siegel joked.

But there was also a feeling of sadness in the air. All of the men talked of other survivors who have died since the last reunion and many more who are no longer healthy enough to travel. Two of the four survivors who were scheduled to speak at the official commemoration ceremony were last minute cancellations due to illnesses; their speeches were read by Buchenwald officials instead. The kinderblock “boys” all understand the importance of this year’s commemoration. “In ten years you’ll be able to count the survivors here on one hand,” Furst said.

This year’s events took place against the backdrop of rising anti-Semitism in Europe and increased sectarian and religious violence around the world, themes that arose often over the weekend. One survivor remembered a fellow prisoner at Buchenwald who believed that whoever survived that hell would live in a paradise, because once people learned about the horrors of the Holocaust, they would lose their desire to kill again. Today, of course, this sounds hopelessly naïve. As we pay lip service to the idea of “never again,” genocide and killings are all too common. Perhaps the need to murder is an intrinsic part of our humanity that can never be extinguished.

Yet the story of Buchenwald’s kinderblock is one of rescue and hope. Antonin Kalina, a non-Jewish, Czech communist, risked his life countless times to save the Jewish boys under his care. As the boys became adults, the majority of them were able to build meaningful lives and families for themselves, denying their tormentors one final victory. Now, nearing the end of their lives, many of them believe that their living testimonies can serve as warnings against how quickly extremism can spread and about how fragile and precious civilization is. The four Kinderblock “boys” spend hours each month visiting schools and talking to students about their experiences during the Holocaust. They consider it their sacred duty before their voices grow forever silent. But with fewer and fewer survivors left, how can we remain vigilant once they are all gone?

As survivors leave the stage, those of us who remain have an obligation to carry on their work. We are the witnesses to the witnesses. Schools and educational institutions such as the Buchenwald Foundation will continue to take the lead in transmitting the lessons of the Holocaust, even after the last survivor is long gone. “Buchenwald is a good thing,” Alex Moskovic, who just celebrated his 82nd birthday, remarked. “They’re teaching the young generation about what happened. There’s enough written and filmed material that they can continue to teach here. If they do the right thing at Buchenwald, this can be done without the survivors.” Films like Kinderblock 66 will continue to be made, thanks to archives of filmed survivor testimony such as the Shoah Foundation’s; the task will be more difficult, but it is both possible and necessary.

Despite the challenges, Naftali Furst is still hopeful. “I wouldn’t have made it this far if I weren’t an optimist,” he said. “The easiest thing to do in Buchenwald was to give up and die.” He plans to be at the seventy-fifth anniversary commemorations in 2020. I hope to be there with him.