When the German Wehrmacht invaded Poland in September 1939, Aleksander Rosner was living in Warsaw with his parents Marianne and Herman Rosner. The Jewish family had to move into the Kraków ghetto in 1941. At the end of 1942, raids became very frequent there. Aleksander’s parents managed to get him smuggled out of the ghetto. He was hidden in Bochnia, east of Kraków.
In 1943 his parents were interned in the Plaszow forced labor camp. They arranged for Aleksander to join them there. Aleksander’s father had to play concerts for the camp commandant Amon Göth. This was how he met the businessman Oskar Schindler, the owner of a Kraków factory where many camp inmates had to work. Schindler decided to help Rosner. He placed Herman, Marianne, and Aleksander Rosner on his list of forced laborers to be transferred to his ammunition factory in Brünnlitz. However, Schindler was unable to prevent Aleksander Rosner and his father being deported to Auschwitz-Birkenau in 1944.
Shortly before the extermination camp was liberated, Aleksander and Herman Rosner were taken to Dachau concentration camp. They were liberated there in April 1945.