 He wrote his first play in 1924 and was later repeatedly imprisoned under Nazi rule in various concentration camps for spreading socialistic anti-war propaganda and being an active member of the Communist Party.From 1937 to 1945 he was an inmate of the Buchenwald concentration camp near Weimar.It was this stay that became the basis for his most famous novel, "Nackt unter Wölfen" (Naked among Wolves).