The Manhattan Project resulted in two nuclear bombs being built for the United States. After several year s of fighting against Japan in the Pacific Ocean, the United States defeated the Japanese and demanded their unconditional surrender. When Japan refused to give up their emperor in the surrender, the President Truman had to make a choice. Either invade Japan or drop the atomic bomb. On August 6th, 1945, Truman ordered the dropping of the bomb on Hiroshima. It caused wide devastation but Japan still refused to surrender. Three days later, Truman ordered the dropping of a second bomb on Nagasaki.