When you stop to think about it, the A Bomb was not a matter of choice.

Early in 1939, the world's scientific community discovered that German physicists had learned the secrets of splitting a uranium atom. Fears soon spread over the possibility of Nazi scientists utilizing that energy to produce a bomb capable of unspeakable destruction.

Scientists Albert Einstein, who fled Nazi persecution, and Enrico Fermi, who escaped Fascist Italy, were now living in the United States. They agreed that the President must be informed of the . . . . .
dangers of atomic technology in the hands of the Axis powers. Fermi traveled to Washington in March to express his concerns to government officials. But few shared his uneasiness.

Einstein penned a letter to President Roosevelt urging the development of an atomic research program later that year. Roosevelt saw neither the necessity nor the utility for such a project, but agreed to proceed slowly. In late 1941, the American effort to design and build an atomic bomb received its code name — the Manhattan Project.   (text source:  http://www.ushistory.org/us/51f.asp

Editor's notes:  Because of the Germans,  we had no choice but to build "the bomb."  And in 1945,  because of the Japs continued aggression,  we had no choice but to drop the bomb  . . . . .   no choice if loosing thousands and thousands of our own soldiers in an invasion of Japan was the alternative.