You might be interested in some threads from the WWII FAQ section on "The atomic bombs":

• There has been some controversy on the true effect of the atomic bombing of Japan. Was it the bomb, or the Soviet declaration of war that ended WWII? - 19 comments, over 2 years old.

• The commenters in this thread showcase the arguments made by in favor of the Soviet influence on the Japanese surrender using diary entries of the Japanese officials and other records that previously had not been looked over in analysis of the issue.

• Why did Japan surrender? - 33 comments, over 2 years old.

• This thread goes into several criticisms of Hasegawa's conclusions regarding the Japanese surrender.

• Are Tsuyoshi Hasegawa's conclusions about the Soviet's influence in triggering the Japanese surrender of WWII widely accepted or are they in dispute? If he got it wrong, how did he get it wrong? - 27 comments, over 2 years old.

• This thread not only gives further criticism of Hasegawa but details how he has been received in the historical community.

There is a lot of speculation and opinion-sharing going on in the top level answers here. As a result the comment/s in question have been removed.

Please be sure to back up any answers to this question with sources, and keep top level comments free of speculation and guesswork.