Austria-Hungary By ExecutiveCouncil Jun 28, 1914 Archduke Franz Ferdinand of Austria-Hungary assassinated in Sarajevo by a Serbian activist. This historic event sparked the start of World War One \ Jul 28, 1914 Austria-Hungary declares war on Serbia. This was the first country to declare war in World War One Aug 10, 1914 -1 September 1914, Austrian invasion of Russian Poland. The fighting between Russia and Austria-Hungary heats up. Sep 15, 1914 Cited, maybe legendarily, as the day trenches are first dug on the Western Front. Dec 1, 1914 - December 17: Battles of Limanowa, in which Austrian forces save their lines and prevent Russia attacking Vienna. Jan 8, 1915 Germany forms a southern army to support the faltering Austrians. May 23, 1915 Italy joined the Allies. The Central Powers lost an ally, but the Allies gained an important one. Jul 13, 1915 -July15, 1915: The German 'Triple Offensive' begins, aiming to destroy the Russian army. Jul 22, 1915 'The Great Retreat' is ordered - Russian forces pull back out of Poland (currently part of Russia), taking machinery and equipment with them. Sep 12, 1915 After the failure of the Austrian 'Black Yellow' offensive, Germany takes over ultimate control of Austro-Hungarian forces. Nov 23, 1915 German, Austro-Hungarian and Bulgarian forces push the Serbian army into exile; Serbia falls. May 14, 1916 - June 10, 1916: Austrian Trentino Offensive against Italy, no gains. Jun 4, 1916 -October 17, 1916: The Brusilov Offensive, an initially successful assault shatters the Austrian army.