The professor at one seminar I attended (a Russian specialists) stated that the bombs were dropped in order to scare the Soviets and basicly bully them into seeing who was the new and only "sheriff in town". To be more precise, to make the Soviets obey the Potsdam Agreements that required new East European governments. The Soviet and Allied perspective was one of "You conquer it, you rule it". Some in the audience were not amused. I had to respect his academic authority, but it sounded revisionist to some in attendance as to why the bombs were dropped.
Thank you for the great student viewing guide.