In the spring of 1945, American forces continued to fight Japan in the Second World War. Germany had already succumbed, with the help of several unexpected Red Army victories on the eastern battlegrounds. The never-say-die Japanese showed no signs of surrendering any time soon. Choosing to fight until death (and not surrendering) was a central belief in Japanese culture. Nonetheless, the United States had a secret weapon: the atomic bomb. America had been motivated to build a nuclear weapon to use in case Germany built their own. .
The Americans believed that Germany had the resources and ability to build a nuclear weapon. It was known that Japan, on the other hand, had a weak scientific base, and thus did not possess nuclear weapons. When Germany surrendered, many political detractors presumed that there was no purpose in furthering attempts to create an atom bomb. Several scientists in a group led by L. Szilard and J. Rotblat even left the Manhattan Project (the group that worked on creating the atom bomb). .
To the U.S. government (Truman) and military, successfully creating a nuclear bomb an important objective. J. Robert Oppenheimer, a physicist that headed the Manhattan Project to create the atomic bomb recalled that "I don't think there was any time where we worked harder at the speed-up than in the period after the German surrender.". It was not long before the atom bomb became reality (completed July 1945). The completion of the atomic bomb left President Harry S. Truman with a difficult decision to ponder: whether or not to drop the nuclear bomb on Japan? It would devastate Japan and almost certainly elicit surrender, and it would also demonstrate the superior power of the U.S.
Truman was seeking a way to end the war in the Pacific that did not require an invasion of Japan, in the interest of saving the lives of U.S. soldiers. Mass invasion would have caused casualties that may have surpassed the death toll at Hiroshima and Nagasaki.