WWII started when Hades got into an argument with Zeus and Poseidon. It started out normally with just the regular argument, ‘Mother Rhea like me the best’ and ‘Sea creatures are better than skeletons and ghosts’ ‘Dead people are better than flying people’ and so on. Finally Hades got incredibly mad and used his son Hitler to do deeds to infuriate Zeus and Poseidon. Zeus and Poseidon retaliated back with Roosevelt and Churchill to harass Hades. Eventually it was an all out war with gods backing either side. A bad choice of decisions led to World War Two and then it was complete pandemonium. End of Story.