World War 1 By kenndyl Jun 28, 1914 Archduke is Assassinated Jun 30, 1914 Russia Mobilizes Their Army Aug 4, 1914 W.W.1. Officially Starts Sep 5, 1914 First Battle of the Marne Oct 19, 1914 First Battle of Ypres Feb 19, 1915 Gallipoli Apr 22, 1915 Gas Is First Used May 7, 1915 Lusitania Sinks Feb 21, 1916 Battle of Verdun May 31, 1916 The Battle of Jutland Jul 1, 1916 Battle of the Somme Sep 15, 1916 Tanks Enter the War Feb 25, 1917 Zimmerman Telegram Apr 6, 1917 U.S. Enters the War Sep 19, 1918 Battle of Megiddo Nov 11, 1918 Armistice Day