 The Congo was also a vitally important economic asset to the Allied powers . The Congo 's gold alone contributed some $ 28 @.@ 5 million to the Allied war effort , while its exports of rubber and uranium provided vital sources of raw materials . Most of the uranium used during the American Manhattan Project – including that used for the nuclear weapons dropped on the Japanese towns of Hiroshima and Nagasaki – was supplied by the Belgian firm Union Minière du Haut Katanga from Katanga Province in the Belgian Congo . 
