World War I By Ashleyp2323 Jun 28, 1914 Assasination of Archduke Ferdinand and his wife. Jul 28, 1914 World War I begins. Apr 22, 1915 German gas attack at Ypres May 7, 1915 128- American citizens died when German submarine sinks the Lusitania Feb 21, 1916 Germans attack at Verdun. Jul 1, 1916 Start Battle of the Somme Apr 6, 1917 United States entered the war. Oct 12, 1917 British attack at Passchendaele. Nov 11, 1918 Armstice ends the war. Nov 30, 1918 A mob lynched obert Pager. Jun 28, 1919 treaty of Versailles sighned.