Recall how World War I broke out after a Serbian nationalist assassinated the Austro-Hungarian archduke in 1914 in Sarajevo, Bosnia. When the Austro-Hungarian Empire declared war on Serbia, Russia came to the defense of its ally. The alliance system kicked in; Germany and the Ottoman Empire joined the Austro-Hungarian, while France and Britain joined Russia. That system is long gone, but the relationship between Russia and Serbia, deeply rooted in ethnic and religious ties, should not be taken lightly.

Recall how Bill Clinton's big war was "Operation Allied Force," conducted by a somewhat reluctant NATO at U.S. insistence in 1999. Building upon NATO's "Operation Deliberate Force" targeting Serbian fighters in Bosnia four years earlier, it resulted in the aerial bombing of a European capital (Belgrade) for the first time since 1945. Human Rights Watch concluded in 2000 that between 488 and 527 Yugoslav civilians were killed as a result of the bombing, which forced Belgrade to obey Washington and withdraw its troops from the heart of the Serbian homeland.

That heart, of course, is Kosovo. Since the seventh century, when the Serbs pressing eastward from Dalmatia established themselves in the old Roman province of Upper Moesia, Kosovo has been the spiritual core of the Serbian nation. The Serbs have shared it with others, notably Albanians, and the Serbian gene-pool is itself complex and changing over time. But Serbian identity was shaped by the Battle of Kosovo Polje (The Field of Blackbirds) against the Ottoman Turks in 1389, in which both Serbian King Lazar and the Ottoman sultan Murad were killed. Modern historians differ about whether this was a draw or heroic defeat of the Serbs; nationalist mythology depicts it as the latter. [...]