1) The war started mainly because of four aspects: Militarism, Alliances, Imperialism and Nationalism
2) It caused the war because Austria blamed Serbia for the killing of the Archduke Franz Ferdinand.
3) A German submarine used in World War I or World War II. During some of Germany's attacks, American passengers were on board of some of the ships. Thus being they felt that action was necessary
4) , the U.S. joined its allies--Britain, France, and Russia--to fight in World War I.
