In the summer of 1939, control of most of central Europe belonged to Hitler and Nazi Germany. Having already taken Czechoslovakia and Austria, Hitler began to turn his attention to the “breadbasket” of Eastern Europe and started to plan how he could gain control of the nation’s there. However, the Sovit Union, a traditional enemy of Germany, stood in the way of further conquests. If Hitler attempted to conquer any territory further east, Joseph Stalin, the Soviet dictator, would certainly declare war on Germany.
Great in depth resource for regular or IB world history.