of Natural Resources, an independent academic institution, were established. A department of mining was established at Tallinn Technical University in 1938. Estonian oil shale industries conducted tests of oil shale samples from Australia, Bulgaria, Germany and South Africa. Developments in German-occupied Estonia Soon after the Soviet occupation in 1940, the entire oil shale industry was nationalised and subordinated to the Mining Office and later to the General Directorate of Mining and Fuel Industry of the Peoples' Commissariat for Light Industry. Germany invaded the Soviet Union in 1941 and the industry's infrastructure was largely destroyed by retreating Soviet forces. During the subsequent German occupation, the industry was merged into a company named Baltische Öl GmbH. Baltische Öl became the largest industry in the Estonian territory. This entity was subordinated to Kontinentale Öl, a company that had exclusive rights to oil production in German-occupied territories. The primary purpose of the industry was production of oil for the German Army. In 1943, after the German troops retreated from the Caspian oil region, Estonian oil shale became increasingly important. On 16 March 1943, Hermann Göring issued a secret order stating that "development and utilisation of Estonian oil shale industry is the most important military-economic task in the territories of the former Baltic states". On 21 June 1943, Reichsführer Heinrich Himmler issued an order to send as many male Jews as possible to the oil shale mining. Baltische Öl consisted of five units (Kiviõli, Küttejõu, Kohtla-Järve, Sillamäe, and Kohtla), all of which were partially restored, previously existing industries. In addition, Baltische Öl started construction of a new mining and shale oil extraction complex in Ahtme, but it never became operational. Prisoners of war and forced labour made up about two-thirds of the work force in these units. While Soviet troops were advancing into Estonia during 1944, about 200 Estonian oil shale specialists were evacuated to Schömberg, Germany, to work at an oil shale industry there, codenamed Operation Desert (Unternehmen Wüste). Shale oil extraction plants in Estonia were destroyed and mines were ignited or inundated by the retreating Germans. Existing oil shale-fired power stations were also destroyed. Developments in Soviet Estonia In 1945–1946 the mining industry was merged into Eesti Põlevkivi (, literally: Estonian Oil Shale; now part of Enefit Power) under the General Directorate of Oil Shale Industry of the USSR (Glavslanets). Shale oil extraction, except the Kiviõli and Kohtla-Nõmme plants, was merged into the