By the early 1900s the notion that a single bomb could destroy an entire city began to take root as physicists developed the science of fission—the ability to create tremendous amounts of energy by splitting the atom. In 1939, as war swept across Europe, president Franklin D. Roosevelt realized that America would soon be drawn into the conflict and the US would be in a race against Germany and Japan to develop the atomic bomb. Under Roosevelt, the Manhattan Project was launched with the goal of developing the atomic bomb and using it to end World War II.