The main rivals are the Serbs and Croats, two Slavic peoples with similar languages - though Serbian is written in Cyrillic and Croatian in Latin script - but whose histories are very different.
The Serbs are Orthodox Christians whose religion was crucial in keeping alive their national identity during almost four centuries of Ottoman Turkish occupation. Of the nations that formed Yugoslavia in 1918, the Serbs were alone in having liberated themselves from foreign rule and set up an independent state in the 19th century.
The Croats spent centuries under the Austro-Hungarian empire and their Catholicism and Central European outlook were equally important in shaping their identity. They resented the fact that the first Yugoslav state, which lasted from 1918-1941, was to a great extent Serbia writ large, with a Serbian king and army and a Serb- dominated political system.
When the Nazis dismembered Yugoslavia in 1941, they created a fascist puppet state of Croatia, which incorporated most of Bosnia. This state slaughtered hundreds of thousands of Serbs and Jews. From 1941-1945 more than a million Yugoslavs died, more than half at the hands of each other.
Tito rebuilt Yugoslavia as a Communist federation of six equal republics, but ethnic antagonisms were never far below the surface. The Serbs disliked Tito's recognition of the Macedonians and the Muslims of Bosnia-Herzegovina as distinct nationalities.
The effect of recognition of the Muslims - Slavs converted to Islam under Turkish rule - and growth in the Muslim population was to turn Bosnian Serbs into a minority in a republic where they had been the largest ethnic group.
The collapse of Communism in 1990-91 led to the election of governments in Slovenia and Croatia committed to independence. Although the Serb-led Yugoslav army tried briefly to prevent Slovenian independence, the Serbs' main concern was Croatia. Croatia had a 600,000-strong Serbian minority, descendants of Serbs who had fled Turkish rule centuries earlier. With the memory of Second World War atrocities behind them, the Serbs were unwilling to live in an independent Croatia again. For their part, the Croats viewed the Serbian minority as a group that had enjoyed special privileges under Communism.
Supported by the army and Serbia itself, the Serbs rose in armed rebellion. They now control about a quarter of Croatia and have set up two autonomous regions that are under the protection of United Nations forces sent in to keep a fragile peace. Croatia has vowed to recapture these regions, by force if necessary.
In Bosnia, three nationalities lived before the latest conflict in inextricably mixed communities: the Muslims with 44 per cent of the population, the Serbs with 32 per cent and the Croats with 17 per cent. The communities lived in relative harmony. After the European Community demanded a referendum on independence in Bosnia in February, the vote split on ethnic lines. Muslims and Croats supported independence but the Serbs boycotted the vote and, again with the army's support, began a fight for territory.
The feature of the Croatian and Bosnian wars that has caught the world's attention has been the Serbian expulsion of Croats, Muslims and smaller nationalities from their native areas in an effort to make the regions purely Serbian. This policy of 'ethnic cleansing' is responsible for the huge wave of Muslim refugees flooding into many European countries. The detention camps where Serbs are holding large numbers of Muslim prisoners are not, however, places of extermination in the Nazi sense. The primary Serbian goal is to remove Muslims from an area comprising about two-thirds of Bosnia so that this territory can be merged into one lump with the two autonomous Serbian regions of Croatia and Serbia proper. This will be 'Greater Serbia'.
At the same time, the Croatian army has helped Croats in Bosnia to take over much of the west of the republic that lies near Croatia's Adriatic coast. Just as the Serbs have declared an 'Independent Republic of Bosnia-Herzegovina', so the Croats have proclaimed an autonomous region of Herzeg-Bosnia with Mostar as its capital. De facto, Croatia has colluded with Serbia in carving up Bosnia, although it has escaped with much less international censure.
The real losers, then, are the Muslims, who have been left with almost no land. Both Serbs and Croats have claimed that Muslims are not a genuine nationality but are 'really' Serbs or Croats beneath their religion. Both have also claimed Bosnia-Herzegovina as part of their own historic territory. The Muslims might once have preferred to stay in a united Yugoslavia where their ethnic and religious rights were protected, but now they are locked in a struggle for their very survival.