What country was most to blame for World War II and why?

Germany is generally given blame for starting the war. However the causes are much more involved than simply blaming 'German aggression'. Hitler said the war was one between the 'have's and have nots'. By this he meant that the club of nations that had empires - Britain, France, Russia and the USA were the have's. The nations that desired empires or were trying to expand their limited ones were Italy, Germany and Japan. The desire of the 'have's' to hang on to their wealth, influence and world dominance clashed with the desire of the 'have nots' to obtain some of those assets for themselves. Japan and Italy were aggressively increasing their empires many years before Germany started expansion. German power was exercised years later but due to greater German military ability, their results were most impressive. Specific events are often shown in history books as the 'start' of WWII such as the German invasion of Poland in Sept 1939 or Pearl Harbor in Dec 1941. With these specific dates it is thus easier to categorize who is to 'blame' for the war - Germany in Poland and Japan in Asia. Such simplistic overviews however, hide the root causes of war - the desire of all nations for economic expansion and cultural dominance of their neighbors.