Archival photo held at the United States Holocaust Memorial Museum in Washington, DC. The undated image shows a group of SS officers posing near Auschwitz. HOLOCAUST MEMORIAL MUSEUM/AFP

"The fact that my great-grandfather was a member of the NSDAP [National Socialist German Workers' Party] was never part of the family story." "I have already found two close relatives, contrary to the family legend that nobody in our family was involved. Changing perspective at 71 is an awful shock." These testimonies, published by Die Zeit in its April 9 edition, are among the thousands of letters received by the weekly publication after it made an extremely user-friendly search tool available online on April 2. For the first time, anyone can explore a trove of over 12 million documents, recording most of the Nazi Party memberships of Germans born before 1926, from 1925 to 1945.

The original file consists of millions of membership cards issued by the NSDAP at the party's main headquarters in Munich or at local branches. Incomplete, the archive was partially saved from destruction in April 1945 by Josef Wirth, a Munich paper manufacturer tasked by the Nazis with disposing of the documents. Recognizing the significance of the collection, he hid the records and later reported his discovery to the American forces, who were occupying the region after the fall of the Third Reich.