Ilse Rewald performed forced labor in the Deutsche Benzinuhren armaments factory in Berlin, from 1941. When her mother and aunt received deportation orders in January 1942, Ilse Rewald and her husband wanted to accompany them. Werner Rewald was not released from his forced labor for the Reichsbahn railroad company, however.
The Rewalds went underground on January 11, 1943. They had to hide separately to begin with. Ilse Rewald spent the first year with Käthe Pickardt and her daughter Ursula. The non-Jewish Berliners Martha Barth and her daughter Lotte Regge supported the Rewalds with food.
After some time, the couple managed to obtain forged identity papers. Fritz Wolzenburg, Werner Rewald’s boss at the Reichsbahn, got hold of Reichsbahn papers with official stamps for them. Ilse Rewald adopted the name of Maria Treptow. She took on various odd jobs to earn money.
In January 1944, Ilse Rewald lost her accommodation with the Pickardts when the apartment was destroyed in an air raid. Hanning Schröder took both Ilse and Werner Rewald into his home in February 1944. They experienced the end of the war there together.