June 28: Assassination of Archduke Franz Ferdinand in Sarajevo

July 23: Austrian Ultimatum is sent to Serbia

July 28: Austria-Hungary declares war on Serbia; Russia begins mobilization

July 31: Germany warns Russia to stop mobilization

August 1: Germany declares war on Russia; Germany and Ottoman Empire sign secret treaty

August 3: Germany declares war on Belgium and France

August 4: Germany invades Belgium; United Kingdom declares war on Germany

August 6: Austria-Hungary declares war on Russia; Serbia declares war on Germany

August 11: France declares war on Austria-Hungary

August 17: Russia enters East Prussia

August 22: Austria-Hungray declares war on Belgium

August 23: Japan declares war on Germany

August 27-30: Battle of Tannenburg

August 30-September 8: Battle of the Marne

October 30-November 11: First Battle of Ypres