Yeah the Nazis did a lot of things...starting WWII was not one of them. Blame the Poles for that one. Poland, using their military that was backed unconditionally by Great Britain, occupied the free city of Danzig, an independent League of Nations protectorate, and then proceeded to uproot all ethnic Germans from the city into internment camps built deep inside Poland. When Poland refused to hand these people over to Germany, Hitler invaded. He then later used those camps as labor camps to support the Nazi war effort.