This chapter talks about the study of workers and labour movements in the First World War. The war demanded total mobilisation in the nations engaged, and in particular in the industries which fed the furnace. The First World War was indeed the first of its kind: no one had imagined anything like it, and there was no previous point of reference to deal with the situations that it created. The nations attempted to remedy the lack of available labour by recruiting foreigners, prisoners of war, adolescents and women. The Hague Convention authorised the employment of prisoners of war, with the exception of officers, provided that the work was not excessive and was unconnected to military operations. The Allied nations retained their legitimacy because they had won the war on the home front and on the battle front.