During the Nazi era, tens of thousands of slave laborers were forced to work in 350 Essen forced labour camps. Here, they did mining work and worked for companies like Krupp and Siemens. Alfried Krupp was convicted in the Krupp trial at Nuremberg for his role in this but was pardoned by the US in 1951. There were several subcamps in Essen in Second World War, such as the subcamps , , .