Before America even entered the war work had been started on the Manhattan Project, a secret project (unknown even to then-V.P. Harry Truman) to develop an atomic bomb. This project began after scientists discovered Hitler's work to split the uranium atom. By 1945, when the atomic bomb was first successfully tested, Germany had surrendered to the Allies in Europe, but Japan’s Emperor still refused to surrender. With the prospect of a million US casualties should they decide to invade Japan, Harry Truman decided to drop the bomb on Hiroshima after a last effort to convince the Japanese to surrender. An added motivator for dropping the bomb was that it would send a clear message to the Soviet Union. Three days after dropping the bomb on Hiroshima, the Americans dropped another nuclear bomb on Nagasaki. The bombs brought about the immediate deaths of 120,000 people with tens of thousands of more to follow. Debate still exists as to whether the United States should have dropped the bombs. As a result of the bombs, VJ Day was declared, ending the war with Japan, but citizens continued to die because of radiation illnesses, and citizens of the two cities had a higher risk of cancer for the rest of their lives.