How misinformed you are. (Or just brainwashed) In both WW I and WW II, Germany had war declared on them. In WW II, it was because September 1, 1939, Germany invaded Poland. And the reason for that was because ethnic Germans there were being murdered. But where was the declaration of war on Russia when they did the same two or three weeks later. Or where was the declaration of war when on November 30, 1939, Russia invaded Finland.
Germany declared war on the U. S. What was the justification for invading the other 10 countries other than Poland? Were France and Britain also killing ethnic Germans?