The atomic bomb was created by Americans during World War II. The atomic bomb was used by splitting an atom which made a huge explosion. This bomb was used in World War II by the Americans against the axis powers. The U.S. dropped this bomb on Hiroshima because the Japanese attacked the U.S. and wouldn't stop until they were all dead or they won. The United States President Roosevelt had to make this very important decision and he chose to drop it. Once he dropped the bomb the war between Japan and the U.S. ended. The choice to drop the bombed saved millions on U.S. lives and also saved resources that would of been used during this war.