"I don't know what they're teaching about Nazis in school these days," Katie, whose grandmother is a Holocaust survivor, tweeted. "But here goes".
Holocaust denial, dragged up in the alt-right tidal wave crashing through the Western world, is alive and well in the highest office of the United States - just one reason why taking time to remember is so important.
Katie's grandmother was just two-years-old when Hitler invaded Poland in 1939, too young to understand that the world was changing around her.
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When she was four years old, she saw that her three-year-old neighbour had been shot by Nazis.
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Months later, she was separated from her family.
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Katie's grandmother went to Majdanek concentration camp for being Polish.
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She was 'adopted' by an officer.
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But her 'adoptive parents' abandoned her when the Allies broke through to Poland.
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She was found in one of the officer's homes days later, barely able to remember her own name.
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Remarkably, the Red Cross reunited her with her family.
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People were grateful for Katie sharing her grandmother's story.
More: This incredible story of a Jewish man who survived the Nazis is a haunting reminder of the Holocaust