 The Congo had become increasingly centralised economically during the Great Depression of the 1930s , as the Belgian government encouraged the production there of cotton , which had value on the international market . The greatest economic demands on the Congo were related to raw materials . Between 1938 and 1944 , the number of workers employed in the mines of the Union Minière du Haut Katanga ( UMHK ) rose from 25 @,@ 000 to 49 @,@ 000 to cope with the increased demand . In order to increase production for the war effort , the colonial authorities increased the hours and the speed at which workers , both European and African , were expected to work . This led to increasing labour unrest across the colony . Discontent among the white population was also increased by the raising of a 40 percent " war tax " . High taxes and price controls were enforced from 1941 , limiting the amount of profit that could be made and curbing profiteering . 
