World War I By Skyethelimit Jun 28, 1914 Assassination Of Archduke Franz Ferdinand Period: Jul 28, 1914 to Nov 11, 1918 World War I May 7, 1915 Sinking of Lusitania Feb 1, 1917 Germany Begins Unrestricted Warfare On The High Seas Feb 24, 1917 U.S. Discovers Zimmermann Telegram Apr 6, 1917 U.S. Declared War On Germany Jun 15, 1917 Espionage Act Passed Nov 10, 1918 Last Day Of Fighting Nov 11, 1918 The End Of The War Jun 28, 1919 Treaty Of Versailles Jun 28, 1919 The League Of Nations Established