From an older answer

Part 1

The problem with the idea of the Balkans as a region especially prone to hatred and with the idea of "Balkanization" or a similar descriptors for this particular reason is the premise. The assertion that the Balkans are a region prone to ethnic conflict or even more prone to ethnic conflict than other regions is a wide spread opinion/stereotype in modern Western Europe and is strongly connected to the construction of that geographical area as somewhat "other" throughout the 19th and 20th century.

Discussing this phenomenon as "Balkanism" historian Maria Todorova writes in the introduction to her book Imagining the Balkans:

[George] Kennan [in his introduction to a 1991 reprint to a 1913 Carnegie Foundation report on the Balkan wars, which was re-published as a commentary on the Yugoslav wars of the early 1990s] has been echoed by a great many American journalists who seem to be truly amazed at Balkan savagery at the end of the twentieth century. Roger Cohen exclaimed "the notion of killing people ... because of something that may have happened in 1495 is unthinkable in the Western world. Not in the Balkans." He was quite right. In the Balkans thy were killing over something that happened in 500 years ago; in Europe, with a longer span of civilized memory, they were killing over something that happened 2000 years ago. One is tempted to ask whether the Holocaust resulted from a "due" or "undue" predominance of barbarity. It occurred a whole fifty years earlier but the two Balkan wars were even earlier. Besides, Kennan wrote his essay only a year after the "neat and clean" Gulf War operation. In seventeen days, American technology managed to kill, in what Jean Baudrillard claimed was merely a television event, at least half the number of total war casualties incurred by all sides during the two Balkan wars. If this is too recent, there was the Vietnam War, where even according to Robert McNamara's In Retrospect "the picture of the world's greatest superpower killing or seriously injuring 1000 noncombatants a week ... is not a pretty one". Whether the Balkans are non-European or not is mostly a matter of academic and political debate, but they certainly have no monopoly over barbarity.

The dripping bite aside, Todorova's point here that it does indeed strike as strange that the Balkans are regularly painted as a particular savage region or a region prone to ethnic conflict when the totality of European history even reaching into the 20th century is full of such examples like the Nazis committing the Holocaust and murdering hundreds of thousands of Slavs, the Austro-Hungarians attempting to kill off the Serbian intelligentsia during WWI, the French war in Algeria, the forceful population exchange between Greece and Turkey, the expulsion of Germans from Eastern Europe, and the conflicts over both Northern Ireland and the Basque regions in Spain carrying on with considerable violently for decades.

As noted, Todorova calls this phenomenon of a discursive formation that understands the Balkan as especially violent and inherently prone to ethnic conflict as "Balkanism", an image frozen in time that is superimposed over the region, its history and especially the conflict of the early 90s. Structurally, she describes it as similar to what Edward Said called "Orientalism", meaning an image permeating media and imagination of the what is deemed the "Balkan" that portrays it a negative category. There are crucial differences though:

The Balkans are concrete, whereas the notion of "the Orient" is vague and intangible; 2.) Orientalism is a refuge from the alienation of industrialization, a metaphor for the forbidden--feminine, sensual, even sexual. Balkanism, on the other hand, is not forbidden or sensual. It is male, primitive, crude, and disheveled; 3) Balkanism is a transitional concept, something not quite non-European, not a final dichotomy; 4) the self-perception of Balkan peoples is not colonial; 5) Orientalism posits Islam as the other, whereas Balkanism deals with Christian peoples; 6) Orientalism is fundamentally racist, categorizing non-white people, whereas Balkanism deals with whites; and 7) Balkan self-identity is itself created against an oriental other.

Some of the most important parts of Todorova's research and writings on the Balkans are that the Balkans as a distinct space are a creation of the 19th century in the sense of its "discovery" by travel literature and politics as an initial space where Christians were oppressed by the Ottomans and that it was especially the Balkan wars and the outbreak of WWI – Gavrilo Princip as the "original sin" of the Balkans – that lead to the region being associated with particular brutality and ethnic violence. While this whole view also bears relevance for WWII, the time of the second Yugoslavia was one during which this idea of the Balkans as particularly violent or prone to ethnic strife almost disappeared, only to make a comeback with a vengeance during the Yugoslav wars of the early 90s.

Crucially, she argues that rather than representing something uniquely "Balkan", the Yugoslav wars of the early 90s represent something very European and Western. Rather than invoking processes that are unique to the Balkans along the lines of "these people have been fighting each other for hundreds of years", these wars are the end point of the ultimate Europeanization of the peninsula. Homogenization in a national and ethnic sense has a long tradition in Europe, e.g. the expulsion of Jews from Spain and England, but with the 19th century forward, this became the prominent notion of European history. In the nineteenth and twentieth centuries the turning of peasants into Frenchmen, the unification of Germany and Italy, the Holocaust, the repositioning of Poland, and even more recent obsessions with cultural purity of "Judeo-Christian" Europe shows that the drive to create ethnically homogeneous states is not exclusively a Balkan phenomenon but rather one that is a factor throughout the whole of modern European history.

In line it is only recently with Dayton that the multicultural state as created/upheld by the international community has made a comeback when before, ti was exactly the ethnic variety of the region that people have seen as negative – Joseph Roucek's "the handicap of heterogeneity." Even the outbreak of the Yugoslav wars are in party related to an international community that aimed at dismantling Yugoslavia as a multi-national state. After all, the arguments by Mock, Genscher and others in encouraging Slovenia, Croatia etc. to become independent and supplying them with political and concrete help to do so were based upon the injustice of the multi-national state and the necessity to achieve the ethnically and nationally homogeneous nation state. The very European and Western notions of order, regularity, and decorum saw ethnic confusion and disorder.

How these conflicts that supposedly prove the Balkanist view actually functioned on the ground can be best shown with the research done by Hannes Grandits in his article Violent social disintegration: a nation-building strategy in late Ottoman Herzegovina. in: Conflicting Loyalties in the Balkans. The Great Powers, the Ottoman Empire and Nation-Building, ed. by N. Clayer, H. Grandits and R. Pichler, London 2010, S. 110–134.

In it Grandits takes a closer look at how the Herzegovinan revolt that eventually lead into Serbo-Turkish and later into the Russo-Turkish wars of 1876–78 actually functioned on the ground. This uprising is often portrayed as both prove for ethnic conflict in the Balkans as well as for the rise of the nation against Ottoman rule in the area. The fact is though that it started out as neither. Rather, it started as something fairly common, a refusal by local political village leaders to pay taxes because the harvest had been bad in previous years.

Initially both sides were open to negotiations and a commission of a Pasha was send to the area to negotiate with the peasants. Within these negotiations however, a group of local nomadic bandits robbed an Ottoman caravan because they feared – rightly – that good relations between authorities and peasants would threaten the support they received from locals. This caravan attack lead to Ottoman reprisals and while things seemed to be winding again down after this, these reprisals caught the attention of young nationalists from Serbia and Montenegro that traveled to the area to enlist the help of aforementioned bandits to fan the flames of conflict. Suffice to say that despite the opposition of local village leaders, they were successful because the spiral of violence this relatively small group of people managed to lead to a homogenization of interests in the sense that local peasants were caught in between fronts and had to declare for one side for fear of retribution or generally violence.

Furthermore, because he saw the chance to gain territory, the Knajz (local ruler) of Montenegro "internationliszed" the conflict by pleading for help from Garibaldi who sent him Italian volunteers to fight with the rebels against the Ottomans. It was really only this move which lead to an internal and external perception of the conflict as one that was "ethnic" or religious while most of the Herzegovians who actually fought on the ground had started this not to end Ottoman rule or "expel the Turk" but rather as rebellion simply to get central authorities to ease off with the taxes.

Through a process of violence and agitation, a relatively small group of what Roger Brubaker describes as nationalist entrepreneurs managed to homogenize the interests of the local population with their own politically goal.