After the death of her daughter Ruth in 1934, Gertrud Marks moved in with her Jewish son-in-law Heinrich Birnbaum. Marks, classified by the “Nuremberg race laws” as a “1st-grade Mischling” (“half-breed”), hid him in her home after he had to go underground. After his arrest by the Gestapo he committed suicide, presumably on January 13, 1943.
Marks also took in her Jewish friend Rudolph Levy-Barley. He was later caught by the Gestapo in February 1944 and deported to Auschwitz, where he perished.
When the Gestapo arrived at her building on March 1, 1943, Marks herself had to go underground. She stayed in various places, including Bad Liebenstein in Thuringia, Saxony, and Silesia. She sold items from her home in order to survive. For a time, she was able to hide in the soldier Walter Moreike’s apartment in Berlin-Neukölln while he was on the front. After her liberation, Gertrud Marks returned to Berlin.