The Battle of Kolubara (Serbian Cyrillic: Колубарска битка, German: Schlacht an der Kolubara) was fought between Austria-Hungary and Serbia in November and December 1914, during the Serbian Campaign of World War I. Both the Austro-Hungarians and the Serbs suffered heavy casualties, with more than 20,000 dead on each side. The defeat humiliated Austria-Hungary, which had hoped to occupy Serbia by the end of 1914. On 22 December, Potiorek and von Frank were relieved of their respective commands, and the 5th and 6th armies were merged into a single 5th Army of 95,000 men.