WWI Events By sweetdimples Apr 4, 1914 Canada is at War Canada is automatically at war against Triple Alliance Jun 28, 1914 assassination of the archduke franz ferdinand Jul 23, 1914 Serbia agrees to two of the three terms of the ultimatum Jul 23, 1914 Austria-Hungary sends ultimatum to Serbia Jul 28, 1914 Archduke and Archduchess visit Sarajevo Jul 29, 1914 Germany declares war on Russia Jul 31, 1914 Germany orders France and Russia to stop mobilizing Aug 4, 1914 Germany invades Belgium Aug 4, 1914 Germany begins the Schlieffen Plan and attacks France through neutral Belgium Aug 8, 1914 Russia mobilizes to defend Serbia Sep 1, 1914 France mobilizes to support its Russian ally Oct 1, 1914 Gavrilo Princip is arrested Apr 22, 1915 Battle of Ypres Jul 28, 1915 Austria-Hungary declares war on Serbia Jul 1, 1916 Battle of the Somme Jan 1, 1917 Beginning of Conscription Crisis in Canada Apr 9, 1917 Battle of Vimy Ridge Jul 31, 1917 Battle of Passchendaele Nov 11, 1918 Armistice Nov 11, 1918 Signing of the Treaty of Versailles Sep 3, 1939 Britain declares war on Germany Sep 3, 1939 Germany declares war on France