Montenegro was a small Balkan tributary state that the Ottoman Turks were never able to subdue completely, for fighting the Turks was a perpetual occupation of the Montenegrins. Its movement toward independence began when its prince-bishop, Danilo II (1822-60), separated the offices of prince and bishop in 1851 and made the throne hereditary. These actions exceeded Danilo's authority since he was a vassal of the Porte (Ottoman government), which sent troops in 1852 to Montenegro. The Montenegrins forced the Turks to retreat after several victories. The war had interested Austria, whose emperor moved troops to the border of Bosnia and Herzegovina and ordered the Turkish commander Omar Pasha (1806-71) to withdraw from Montenegro, which the Turks did in 1853 after Russian pressure was added. No formal treaty was concluded.