What motives were behind the United States decision to use atomic bombs against Japan?

Since 1945,
the US decision to drop atomic bombs on Hiroshima and Nagasaki has been the subject of
tremendous controversy.  However, at the time, there was little controversy over it.  The bombs
were essentially seen as another tool of war that could and should be used to bring an end to
the war as quickly as possible.

Since 1945, people have suggested that the
US had ulterior motives for using the bomb and that it should have tried other options.  People
suggest that the US dropped the bomb so as to scare the Soviets and to make them...