World War I By HudsonD May 28, 1914 Austria-Hungary declare war on Serbia Jun 28, 1914 Franz Ferdinand Assassination The assassination of Archduke of Austria caused the beginning of World War I Apr 1, 1915 First use of a gas weapon by the Germans May 7, 1915 Sinking of the Lusitania Oct 1, 1916 Wilson re-elected; pledged American neutrality Jan 1, 1917 Zimmerman note Apr 1, 1917 U.S. declared war Oct 1, 1917 Bulsheviks led by Lenin overthrow Russian government Oct 11, 1918 War ends Apr 28, 1919 Treaty of Versailles
