One key aspect leading up to WWI is the many alliances that were created. France, England and Russia had an alliance. Germany, Austria-HUngry, and Italy also had an aliance. Because of these aliances, if one country attacked another, through the various treaties all of the other countries would be dragged in. WIth modern warfare being added into this, WWI was a very deadly war. Since almost all countries were involved, all of Europe became the battlefield. Europe had no seen a continent wide war since Napoleon about 100 years earlier.