The Cold War, for all its intrinsic dangers involving the potential for large-scale nuclear war and the consequent decimation of Europe and the United States, provided a stabilizing structure that precluded the outbreak of the kind of regional conflict that had dominated European history for hundreds of years. The East versus West framework that existed from the end of the World War II to the 1989 fall of the Berlin Wall saw the longest sustained period of peace in modern European history.
Absent the stabilizing influence of the Cold War, the age-old problem of political strife in the Balkans reemerged. In Central Europe, Czechoslavakia managed a peaceful break-up into the Czech Republic and Slovakia, but Yugoslavia, previously held together by the iron grip of the dictator Josip Broz Tito, whose death in 1980 presaged the eventual disintegration of the country, harbored far more intense ethnic and religious divisions that couldn't survive Tito's death and the end of the Cold War.
Yugoslavia was a federal system in terms of the central government holding together diverse nationalities. Once the central government was weakened, the fissures were exploited by nationalistic politicians employing racial and religious prejudices to buttress their positions. Eastern Orthodox Serbia, with its Communist orientation, and Croatia, with its fascist background, both sought to subjugate Muslim Bosnia-Herzegovina. The Bosnia war that ran from 1992 to 1995 was a protracted and bloody reminder of the depth of hostilities that continued to pervade the Balkans.
The July 1995 massacre by Serbian militias of thousands of Bosnian Muslim men and boys who had been rounded up and held in the town of Srebrinica, despite the presence of United Nations peacekeepers, served as the symbol of the barbarity that survived World War II in a Europe that many had hoped had put that level of racially-motivated, government-sponsored killing behind it. The massacre also served as a stark signal that the United Nations, formed in the aftermath of World War II to prevent such conflicts, had failed in its central mission.
The Dayton peace agreement, so called because of the Dayton, Ohio, location of the ultimately successful diplomatic efforts at ending the conflict, stopped the fighting, but the former country of Yugoslavia had not seen the end of ethnic conflict.
The Serbian province of Kosovo, with its majority Albanian Muslim population, sought independence from Serbia. The Kosovo Liberation Army, a militia formed in 1991 to fight Serbian dominance (and it needs to be reminded that Kosovo, despite its contemporary Albanian Muslim majority, is a deeply important to Serbs as the site of a major battle between Serbs and Ottoman Turks and is considered the cradle of Serbian civilization) began to increase attacks on Serbian villages. The consequent fighting between the Kosovo Liberation Army and Serbia that ran from February 1998 to June 1999, was brought to an end only with U.S. military intervention on the side of the Albanian population. U.S. airstrikes against Serbia convinced that country's leader to cease its offensive against Kosovo, and the latter would emerge as an independent country.
These conflicts were a sad wake-up call to Europeans, who had hoped that the modern era had seen the end of genocidal fighting.