The First World War began on 28 July 1914 when Austria-Hungary declared war on Serbia. Most of the subsequent Balkan offensives occurred near Belgrade. Austro-Hungarian monitors shelled Belgrade on 29 July 1914, and it was taken by the Austro-Hungarian Army under General Oskar Potiorek on 30 November. On 15 December, it was re-taken by Serbian troops under Marshal Radomir Putnik. After a prolonged battle which destroyed much of the city, starting on 6 October 1915, Belgrade fell to German and Austro-Hungarian troops commanded by Field Marshal August von Mackensen on 9 October of the same year. The city was liberated by Serbian and French troops on 1 November 1918, under the command of Marshal Louis Franchet d'Espèrey of France and Crown Prince Alexander of Serbia. Belgrade, decimated as a front-line city, lost the title of largest city in the Kingdom to Subotica for some time.