1938 Germany is growing stronger, the nazi's are starting to become a threat, France and England are worried, and Stalin having read Hitlers book decides he is a threat and in a moment of panic or paranoia orders the March 13th invasion.
This started a war that would consume an entire generation much like the great war before it had. Nazi Germany and Communist Russia would fight a lengthy death battle with conventional and unconventional phases that would continue for decades. Even to this day the relationship between the two countries is utterly toxic. Poor Poland stuck in the middle of this madness would be devastated. Meanwhile France and England were able to sit out the madness slowly regaining their past strength.
But what if the war had gone differently? Hitler had been planning on hitting the West first before turning his attention on Russia, what if he had gotten the chance to be the aggressor in the conflict? What if the russians had not started the second great war?