In the Second World War the loss of 60% of the mining areas to German invaders forced the rapid expansion of mines in the Urals, as well as greater use of mines in the Kuznetsk Basin in Siberia. In 1939 the Urals produced only half the fuel needed by local industry. During the war the mines were expanded and over 700 factories were evacuated from the west, greatly increasing the demand for Ural coal. Prisoners from the Gulag were sent to the mines; up to a third of the workers were women. The miners were given much higher rations of food. Output doubled and the share of the region in the total national coal production rose from 8% to 22%.