World War I began when Austria-Hungary invaded Serbia in July 1914, following the Assassination of Archduke Franz Ferdinand by Gavrilo Princip. Austria-Hungary was one of the Central Powers, along with the German Empire and the Ottoman Empire. Austro-Hungarian forces fought the Allies in Serbia, on the Eastern Front, in Italy, and in Romania. With heavy aid and support from its allies, the empire managed to occupy Serbia in 1915 and force Romania out of the war in 1917. On the other fronts, it suffered severe casualties, culminating in the collapse of the Italian front, which led the Austrians to accept the Armistice of Villa Giusti on 3 November 1918.