The biggest difference is that the majority of the material used to compile Shattered Sword was taken from information that was documented as things unfolded not years after the event. However you look at it giving up was the Emporer's call; wether he reached that decision unilatterally or through a quorum of his cabinet and advisors. The point is that whom ever came to the conclusion the finally give up they could have done so much sooner that 12, Aug. 1945. After the capture of Okinawa the Japanese public was faced with the realisation that there were going to be foreign boots on Japanese soil and they would have to make the choice of surrendering or dying to preserve the Emporer. The attitudes in 1939 were very different than those of 1945. As far as Russia's post war intentions in Europe the writing was on the wall after the Yalta Conference, any doubt was removed after Potsdam.