In September 1939, 3.3 million Jews lived in the Republic of Poland. In 1945, only 300,000 were still alive. Polish Jews were more than half of the victims of the Holocaust. Additionally, hundreds of thousands of Jews from all over Europe were taken to Poland to be killed there. Sources on the Holocaust in Poland are thus central to EHRI’s mission. Despite widespread destruction, countless sources do survive in the country itself as well as across the world. Although the task of gathering information about these holdings with its many different languages, source types, and archival systems is quite daunting, EHRI made it one of its priorities.