But, Mr. Alperovitz argues, Truman and his Secretary of State, James F. Byrnes, were struck by the notion that ending World War II without dropping the atomic bomb would not have brought added strength to American diplomacy against the Soviet Union in Europe.
The debate goes on.
Did We Need to Drop It? - NYTimes.com
The US decision to drop atomic bombs on Hiroshima and Nagasaki in 1945 was meant to kick-start the Cold War rather than end the Second World War, according to two nuclear historians who say they have new evidence backing the controversial theory.
Hiroshima bomb may have carried hidden agenda - science-in-society - 21 July 2005 - New Scientist
Some military analysts insist that Japan was on its knees and the bombings were simply unnecessary.
The Decision to Drop the Bomb [ushistory.org]
In the end, none of these alternatives were chosen. However, it does not rule out their possible efficacy nor does it mean that the atomic bomb was the only way to produce surrender by the Japanese.
Understanding the Decision to Drop the Bomb on Hiroshima and Nagasaki | Center for Strategic and International Studies