Unfree labour is a labour toled to do against one's will or a situation when someone is being told to work without payment. Some of the time the term is talking about slavery.
Unfree labour is prohibited by Universal Declaration of Human Rights and international law on human rights, as well as the conventions No.29 and 105 of the International Labour Organization.
Conscription, forcing people to join the army and to fight, even if they do not want to do so, can be considered as unfree labour.
Images for kids
Convict labourers in Australia in the early 20th century.
Prisoner labour at the construction of the White Sea–Baltic Canal, 1931-1933
Female forced laborers wearing "OST" (Ost-Arbeiter) badges are liberated from a camp near Lodz, January 1945.