In the summer of 1942, the friends began to question and resist the principals and policies of the Nazi regime. The group decided to adopt the strategy of passive resistance that was being used by students fighting against racial discrimination in the United States. This included publishing leaflets calling for the restoration of democracy and social justice. These were distributed throughout central Germany and the Gestapo soon became aware of the group's activities. The group co-authored six anti-Nazi Third Reich political resistance leaflets. Calling themselves the White Rose, they instructed Germans to passively resist the Nazis. They had been horrified by the behaviour of the Germans on the Eastern Front where they had witnessed a group of naked Jews being shot in a pit. Sophie Scholl at varying stages of her life The core of the White Rose consisted of students; Hans Scholl, Alex Schmorell, Willi Graf, and Christoph Probst, all in their early twenties. Also members were Hans and Sophie's sister Inge Scholl, and a professor of philosophy, Kurt Huber. Sophie also joined the group, however contrary to popular belief, she was not a co-author of the articles. Her brother had been initially keen to keep her ignorant of their activities, but once she discovered his activities, she joined him and proved invaluable to the group: as a female, her chances of being randomly stopped by the SS were much smaller. Between June 1942 and February 1943, they prepared and distributed six different leaflets, in which they called for the active opposition of the German people to Nazi oppression and tyranny. Several of the group members had been deployed to the Eastern Front for military service during the academic break. In late fall the men returned and the White Rose resumed its resistance activities. In January 1943, using a hand-operated duplicating machine, the group is thought to have produced between 6,000 and 9,000 copies of their fifth leaflet, "Appeal to all Germans!", which was distributed via courier runs to many cities (where they were mailed).