January 27 is International Holocaust Remembrance Day. The date was chosen because it marks the day in 1945 that Auschwitz, Nazi Germany's largest concentration and death camp, was liberated by Soviet troops, revealing the horrors within.
The United Nations is commemorating the day with an event that will be livestreamed.
According to History.com, Soviet troops thought the camp in southern Poland was empty, but they were wrong.
"Auschwitz seemed silent and abandoned at first, soldiers soon realized they were filled with people-thousands of them, left to die by SS guards who evacuated the camps after trying to cover up their crimes. As they saw the soldiers, the emaciated prisoners hugged, kissed and cried."
Six million Jews were systematically killed by the Nazis in World War II
Other groups were also targeted, according to the Council of Europe, for "their perceived racial and biological inferiority. These included Roma, disabled people, Soviet prisoners of war and homosexuals. Others, such as Jehovah's Witnesses, Socialists and Communists, were targeted for their religious or political beliefs."