Although a pursuit to Prizren was conducted that was left largely to the Bulgarians. Conditions would simply not support the use of large forces. The IV Reserve Corps in Priština had to go on half rations. The Austro-Hungarian Tenth Mountain Brigade found its route south from Ribaric blocked by a 4,921-foot high mountain with a completely iced over track as the only way through. The brigade had already lost 30 men who had frozen to death in the harsh conditions. Confronted by these stark realities, Mackensen declared an end to the campaign on November 24, 1915. Berlin declared the campaign over on the 28th. All of old Serbia had been overrun, and after only three years, Kosovo was once more in the grip of an invader. On 25 November, the Serbian High Command issued its official order to retreat, through the mountains of Montenegro and Albania, and join the Allies to continue the war out of the country. The Serbian High Command came to the conclusion that its army was not in a favorable position and condition for a counterattack, but more importantly that capitulation was a worse choice. The last rearguard action took place at Prizren on the 27th; the defenders subsequently withdrawing down the Drin River Valley and over the Albanian frontier. Mackensen elected to not follow. Following this battle and into early 1916, over 400,000 defeated and worn-out Serbian soldiers and civilian refugees, with thousands of Austrian prisoners, retreated toward the Adriatic coast on a terrible trek across Prokletije, the Accursed Mountains, that separate Kosovo and Albania, as the snow began to fall. They retreated in three columns, one across southern Montenegro, one through central Kosovo across northern Albania, and the southernmost from Prizren to the port of Dürres. Ravaged by disease, freezing to death in the bitter winter, lacking food or transport, harassed all the while by Albanian guerrillas, the survivors managed somehow to stagger to the Albanian coast in what became known as the “Great Retreat.” The territory of Serbia was occupied by Austro-Hungarian and Bulgarian troops. In the Austrian zone of occupation (northern and central Serbia), a governor-general was established with a center in Belgrade. In the territory occupied by the Bulgarians, a governor-general was established with a center in Niš. Kosovo was divided between the Austrians and the Bulgarians - the Bulgarian army occupied the eastern regions, while the Austro-Hungarian occupied the western regions.