This article analyzes the work relations and the composition of the work force in the Bor copper mine in German-occupied Serbia (1941-1944). The exploitation of that mine was one of the most important projects for the German war economy in Southeastern Europe. The Serbian collaboration government introduced several decrees regulating the labor market and labor service to the effect that pre-war work forces were supplemented by mostly unqualified workers from other Serbian regions. When the situation deteriorated during the war, resistance movements grew, and motivation of workers was fading. As a reaction, other ethnic groups were recruited for forced labor in the mine, among them Hungarian "Work Jews," Soviet prisoners of war, and Italian military internees. The local workers, the groups later deployed in Bor, and the camp personnel (guards, administration) thus were of a characteristic multi-ethnic composition. The article includes some methodological considerations about the use of concepts in historiography such as resistance, collaboration, freedom, and force.