It was her performance for the Germans at the One Two Two Club, however, which made Piaf a symbol of the French Resistance Movement. As a reward for her performance, the Germans allowed Piaf to pose for pictures with French war prisoners to boost the prisoners’ morale. When the prisoners received their individual photos, they were able to cut out their own images and use them to forge identity papers as part of their escape plan. Thus, Piaf, although indirectly, helped save the lives of many French prisoners during World War II.
Source: Ultra Facts