Austria-Hungary was a European great power, with a great interest in Balkans. Serbia had gained independece from Ottoman Empire, and wanted to help Serbs and other Slavic people in areas occupied by Austro-Hungary. So there was a clear conflict of interests. Serbia had fought for independence from the Ottoman Empire since about 1804 and gradually enlarged its territory. In 1878, the European great powers made the contested and potentially very explosive area of Bosnia-Herzegovina an Austrian protectorate, in the hope of keeping the area out of harms way.
Serbias AlliesIn WWI the allied forces (Britain, France, and later on America and Italy) were all allied with Serbia against the Austro-Hungarians and the Germans. In the middle ages, the Byzantine Empire was the Serbian Empires friend. When Serbia was occupied by the Ottomans, Austria, Poland and Venice helped Serbia. During the first Balkan War, Bulgaria and Greece were allies. During the 2nd Balkan War, Serbia allied with Greece. During the WWI, besides those already listed, Serbia also allied with Russia, traditional friend to Serbia. During WWII, Serbian allies included the UK, Russia, the United States, France, and other anti-fascist countries. After WWII Serbia was part of Yugoslavia, a non-allied country balanced between East and West. During 1990 Serbia did not have many friends, but now old allies are back, primarily Greece, France and the Russia . Curiously, Serbia has never had conflict with its two neighbors: Greece and Romania.Even though some serbian politicians try to get Serbia inside Europian Union most of the common serbs blame the west for the desperate situation in whitch Serbia it is now.Serbia isnt and never will be allies with NATO or america!!
Politics. Because like Croatia, they wanted to make a new country, new language and new flag as kosovo is trying and when they split up it was the saddest day for serbians in Montenegro. people were crying for weeks.
Serbia and serbs have much hatred.. (surprise, surprise) But i know for a fact that Albania and Albanians have a very strong hatred for Serbs, as do Croatians and Bosnians and other Ex-Yugoslavian countries/republics who have been through war with Serbia..