At the onset of World War II, Helena Flaum, 12 at the time, lived in Rawa-Ruska, Poland, not far from the Ukrainian border. After Germany invaded, she moved into the town’s ghetto until the Nazis began transporting Jews to concentration camps.

When Holocaust survivor Claire Boren was a child, she and her mother spent months hiding in a hole dug under a pig sty — “about the size of a coffin,” she remembers — barely large enough to hold the two of them.