Adam Loss came from a Polish Jewish middle-class family. He lived in Gdynia with his parents Franciszka and Grzegorz Loss and his older sister Regina. After the war began in 1939, they returned to Adam’s birthplace of Baranowicze (now Baranavichy).
After the German Wehrmacht occupied Baranowicze in June 1941, the family was subject to persecution. In the fall of 1941, 13-year-old Adam Loss and his family had to move to the ghetto, where they often went hungry. During the mass shootings in the ghetto, they retreated to hiding places they had built themselves. When his father was murdered during a raid in 1942, Adam Loss fled the ghetto with his mother and sister. They hid in nearby villages after their escape. The Tatar family Chazbijewicz and other Polish and Belarusian farming families provided them with food and accommodation. However, they frequently had to sleep in forests or fields.
Adam Loss joined a Soviet partisan group in 1943. He survived the war. In 1945 Poland had to cede its eastern territories to the Soviet Union, and Baranowicze became part of Belarus. Franciszka, Adam, and Regina Loss therefore moved to Poland. Adam Loss emigrated to France in 1946.