In 1945 Allied troops freed prisoners from Nazi concentration camps. In these camps, millions of Jews and other prisoners had been killed or had died from hunger, disease and cruelty.
It's thought 6 million Jews were killed. Among the victims were many children. One young girl left a diary of her life in hiding, before she was captured. Her name was Anne Frank. She died, aged 15, in 1945 at the Bergen-Belsen prison camp.