Many events will mark this year’s 70th anniversary of the end of World War II. One of the most poignant occurred last month, when Holocaust survivors returned to Poland to commemorate their release from the Auschwitz concentration camp.

The horrors they suffered are recounted in a new HBO documentary, “Night Will Fall,” which, like “Selma,” the theatrical film depicting a seminal moment in the civil rights movement, should be seen by a much wider audience.

“Night Will Fall” includes footage of Holocaust victims being freed and details the depravities of their Nazi captors. It also shows the seemingly good people who pretended they were unaware of the atrocities occurring not that far away from their bucolic villages.

Much of the documentary was taken from an earlier film, “German Concentration Camps Factual Survey,” which the Allies began making in 1945 but never released. Apparently, the British and Americans decided that causing the Germans to feel more guilt about the millions of emaciated, brutalized bodies discovered in the concentration camps would crush their morale, and defeated Germany was already being considered as a potential ally against the increasingly bellicose Soviet Union.

The HBO documentary’s title is from a line spoken by a narrator in the unreleased World War II film: “Unless the world learns the lesson these pictures teach, night will fall.” Or as George Santayana put it, “Those who cannot remember the past are condemned to repeat it.”