Service du travail obligatoire

The Service du travail obligatoire (STO; lit. 'compulsory work service') was the forced enlistment and deportation of hundreds of thousands of French workers to Nazi Germany to work as forced labour for the German war effort during World War II. The STO was created under laws and regulations of Vichy France, but it was used by Nazi Germany to compensate for its loss of manpower as it enlisted more and more soldiers for the Eastern Front. The German government promised that for every three French workers sent it would release one French prisoner of war (POW).

Source: Wikipedia — Service du travail obligatoire (CC BY-SA 4.0)