What was the long range and immediate cause of the 1st world war?

what was the long range and immediate cause of the 1st world war? how did world war one change the nature of warfare? please elaborate.|||Mutual offense alliances between russia and serbia, Germany and Austria-Hungary, France and Russia, Britain france and belgium, and japan and britain. Also European Imperialism, Nationalism, Militarism, and the assassination of Archduke Franz Ferdinand