World War I By mrslocomb Jun 28, 1914 Archduke Francis Ferdinand Assassinated Period: Jun 28, 1914 to Nov 11, 1918 World War I - Key Events Sep 9, 1914 First Battle of the Marne Begins Oct 14, 1914 First Battle of the Ypres Begins May 7, 1915 Sinking of the Lusitania Feb 21, 1916 Battle of Verdun Begins Jul 1, 1916 Battle of the Somme Begins Feb 24, 1917 Zimmermann Telegram Apr 6, 1917 US declares war on Germany Sep 26, 1918 Meuse-Argonne offensive opens Nov 11, 1918 Armistice Day
