After Belgium had surrendered to Nazi Germany on 28 May 1940, His Excellency Pierre Ryckmans, Governor-General of the Belgian Congo, decided that the colony would continue to fight on the side of the Allies. With Belgium occupied, the contribution to the Allied cause by the Free Belgian Forces from the Belgian Congo was primarily an economic one providing copper, wolfram, zinc, tin, rubber, cotton and more. Already prior to the war uranium from the Shinkolobwe mine had been shipped to New York; it was later used in the Manhattan Project to produce the atomic bomb for Hiroshima. The military contribution was also important: the "Force Publique" grew to 40,000 in the course of the War, formed into three brigades, a river force and support units. It provided detachments to fight Italian forces during the East Africa Campaign and serve as garrisons in West Africa and the Middle East.