Who was behind it? All the power hungry psychopaths that liked Hitler´s ideas of course. \n\nThere also was a secret part to the Hitler-Stalin-pact that came into place after the german invasion from the west - the red army came from the east and forced the polish government into fleeing to Rumania. Shortly after that Poland was divided between the two forces. \n\nWhat was behind it was simple - Hitler wrote in his book "Mein Kampf" that either Germany would be worldleaders or would not be at all.... so world domination was the foremost reason behind it. \nClever enough, german SS forces dressed up as polish freedomfighters and attacked the german radiostation in Gleiwitz near the polish border and declared war with Germany while posing as polish forces. With this one and a couple of other attacks they tried to justify attacking Poland shortly after. \n\nBTW, it is not true that Germany had no colonies, actually St. Thomas was a German colony (now US) just like Crab Island in the caribbean and Ghana used to be Groß Friedrichsburg. Those days were gone in the 1930s but yes, Germany had colonies.