Conflict among the people of the Balkans has occurred for centuries. Most citizens of the former Yugoslavia —a country about the size of the state of Wyoming — can trace their ancestry to Slavic tribes whose members migrated from northern Europe in the seventh century. Yet a combination of outside influences helped create enormous differences among the country's various ethnic groups. As Pulitzer Prize-winning journalist Roy Gutman writes, "The history of the people of the Balkans is a tangle of legend and myth, of claims and counterclaims over who did what to whom and when." That tangled history has been marked by clashes as bloody as the war that has ravaged Bosnia in recent times.

A Region Divided

Details about the southern Slavs who occupied the Balkan Peninsula are sketchy. Historians believe they were a warlike people who settled into three...