The history of the Balkans is written in blood. The Serbs and Croats have hated each other for centuries, the Hatfields and McCoys of a murderous backwater that has long threatened the peace of Europe (box, page 34). Now the region where World War I began could present Europe with its first big conflict of the post-cold-war period. This time there is a crucial difference: the outside world is not taking sides. Still, the potential civil war in Yugoslavia is a kind of problem for which there are no solutions yet in George Bush’s “new world order” or Mikhail Gorbachev’s “common European home.” “We can be confident that it won’t lead to World War III,” says a senior U.S. official who knows the Balkans. “But we can’t be confident where it will lead.”

The crisis in Yugoslavia also may set a bad example for nationalists and central governments in other countries with disgruntled minorities: the Slovaks in Czechoslovakia, ethnic Hungarians in Romania and the Baltic peoples of the Soviet Union. “The unilateral secessions and the use of violence to put them down have both sent the wrong signal to other countries,” says a Washington official. “If either course of action is rewarded, that signal becomes more dangerous.”

The declarations of independence by Croatia and Slovenia provoked an uneven military response by Yugoslav authorities. Federal forces in Croatia were careful not to pick any fights. In little Slovenia, federal forces went on the offensive, seizing posts on the borders with Italy, Austria and Hungary, bombing airfields and strafing civilian traffic on highways. The Slovenes said more than 100 people were killed or wounded. After some bitter fighting last Friday, both sides agreed on a 90-day cease-fire. But continued violence led a senior Army general to warn that federal forces would take “decisive military action” if the Slovene rebels kept on fighting.

In a shaky deal patched together by the European Community (EC), Slovenia and Croatia promised to “freeze” their declarations of independence for the duration of the cease-fire. Croatian representative Stipe Mesic was allowed to take his turn as head of Yugoslavia’s eight-member collective presidency, a rotation that had been blocked by Serbia, the biggest and most powerful republic. The agreement put Mesic at least nominally in command of the federal Army, officered mostly by Serbians, which had been acting more or less on its own while the presidency was paralyzed. It appeared that Croatia, which rejected communism in free elections last year, might yet be persuaded to remain in a looser new Yugoslav federation, despite the fact that its archrival, Serbia, is still ruled by hard-line former communists.

The democratic, pro-Western Slovenes insisted they would never give up full independence. “I can see no democratic way through which Slovenia can be part of Yugoslavia,” said President Milan Kucan. With less territory than Maryland and only 2 million of Yugoslavia’s 24 million people, Slovenia may have trouble standing on its own. But Foreign Minister Dimitrij Rupel insisted: “There is no question of renouncing independence. During the 90 days, we will refrain from taking further steps to implement our independence. But the agreement does not postpone what we have already announced.”

One way or another, the artificial unity imposed on Yugoslavia by Communist dictator Josip Broz Tito could well be finished. The falling-out began with Tito’s death in 1980. By last month, when Secretary of State James Baker met with the leaders of all six republics during a visit to Belgrade, Tito’s heirs were at one another’s throats. The Americans were appalled by the emotional and reckless talk they heard. When Baker warned the leader of Montenegro, Serbia’s hard-line ally, that strife in Yugoslavia could be a disaster for the region and for Europe as a whole, the Montenegrin replied: “Mr. Secretary, I’m prepared to take that risk.”

These are small men, petty chauvinists who are prepared to launch a Balkan war without regard to the consequences," says a senior U.S. official who accompanied Baker on the trip. The Americans were particularly fed up with Serbian strongman Slobodan Milosevic, who blocked Croatia’s turn in the presidency. Said one: “I have watched for too long the narrow interests–promoted in good part by that s.o.b. Milosevic–overcome the broader interests of that country.”

After the declarations of independence, the European Community, which held a summit in Luxembourg last week, sent a three-man team to Belgrade to get negotiations started. But the West Europeans were not entirely in agreement among themselves. Germany emphasized the plight of minorities, with Chancellor Helmut Kohl defending “the right of self-determination.” Britain and France put stronger emphasis on holding Yugoslavia together. “The community should not be opposed to self-determination,” said French President Francois Mitterrand, “but neither should it be accused of treating territorial integrity lightly.”

In addition to the EC peacemaking efforts, the Conference on Security and Cooperation in Europe (CSCE), a loose alignment of 33 European nations plus the United States and Canada, was expected to hold an emergency meeting on Yugoslavia this week. There was a widespread feeling that Europeans were obliged to do something about the crisis in their own backyard. “This is the hour of Europe,” said Luxembourg’s Foreign Minister Jacques Poos, one of the EC emissaries to Belgrade. “It is not the hour of the Americans.”

All-out civil war seems less likely than a long and occasionally violent muddle. On paper, the federal Yugoslav Army, with 180,000 active troops and 510,000 reservists, looks strong enough to overwhelm the Slovenes - and the Croats, too, if it comes to that. In reality, the Army is riven by the same divisions that threaten the rest of Yugoslav society. The Slovenes said they took in 525 prisoners and 250 federal defectors last week. The federals would face similar problems, and perhaps on a much larger scale, in any civil war.

Although their little country looks like a mouse trying to roar, Slovenes insist they are ready to fight on. “We have been buying antitank and antiaircraft weapons for more than a year,” says Slovenian government spokesman Jelko Kacin. “We bought everything needed to fight off an occupation,” he says, adding that most of the weapons, including mines and shoulder-fired missiles, come from Singapore and are suitable for the lightly trained militiamen defending Slovenia. “They are cheap, efficient and effective,” he says.

The Slovenes may be hoping that, under cover of all the confusion that is likely in the months ahead, they will be able to slip away to full independence. A country of tidy farms and pristine industrial parks, Slovenia is an economic powerhouse, producing a quarter of Yugoslavia’s gross national product with 8 percent of its population. “We can go it alone,” says Josip Skoberne, head of the chamber of commerce in Ljubljana, the republic’s capital. Croatia seems less bullish on full independence, if only because its large Serbian minority would fiercely resist a break with Yugoslavia. If both sides behave sensibly - a very big “if” in the Balkans - Zagreb and Belgrade may yet be able to compromise on a new form of confederation - a deal too good for even the Slovenes to turn down. That possibility is perhaps the best reason to hope that a civil war in Yugoslavia can still be averted.

From the fourth century on, the Balkans have been a violent fault line between East and West, the scene of epochal struggles: Rome versus Byzantium, Christianity versus Islam, the empires of Europe versus the empire of the Turks. In 1914, as the old order crumbled, the Balkans provided the spark that touched off World War I. Herded together in a new country, the Balkan nationalities spent World War II slaughtering one another in even greater numbers than they were slaughtered by the Nazis. For the next 35 years a Communist strongman papered over the rifts. Now the Balkans are boiling again. Some moments from the history of a divided land:

Theodosius I divides the Roman Empire into two parts. The Latin-speaking Western Roman Empire includes what are now Croatia, Slovenia and Bosnia. The Greek-speaking Byzantine Empire includes what are now Macedonia, Montenegro and Serbia. Germanic tribes soon overrun much of the Western Empire.

Austria’s Hapsburg monarchy solidifies its control of Croatia and Slovenia; Serbia and other southern states are governed by the Ottoman Turks. The north is Catholic and uses the Roman alphabet; the south is Eastern Orthodox and writes in Cyrillic letters.

Serbia gets its independence as part of the Treaty of San Stefano, which concludes a war between Russia and Turkey. Serbia, which fought the Turks, tries to form a united Slavic state with Slovenia and Croatia, a centuries-old goal. Austria-Hungary refuses to relinquish its Slavic possessions, and extends its control also over Bosnia and Hercegovina as part of an agreement with Russia and Germany to share influence over the Balkans. Serbian King Milan Obrenovic is powerless to resist. He sets up a constitutional monarchy in 1889.

A Bosnian Serb, enraged by Austria-Hungary’s annexation of Bosnia, assassinates Austrian Archduke Francis Ferdinand and his wife. Austria-Hungary accuses Serbia of complicity. It declares war on Serbia and ignites World War I, which costs Serbia nearly a quarter of its population. In 1918 the Austro-Hungarian Empire dissolves; the Kingdom of the Serbs, Croats and Slovenes is proclaimed, uniting the northern and southern provinces.

King Alexander assumes the role of dictator, changes the country’s name to Yugoslavia and brutally represses nationalism in the Balkans.A Croatian separatist movement resists. A Macedonian terrorist assassinates Alexander in 1934. Germany defeats Yugoslavia in 1941. During World War II, a fascist puppet government in Croatia kills some 350,000 ethnic Serbs. Afterward, communist partisans kill 100,000 Croatian prisoners of war.

Yugoslavia becomes a communist state under Josip Broz Tito, who led the partisans. A Croat, he fosters a cult of personality to suppress the Serb-Croat rivalry. In 1980, Tito dies. Separatist movements gather strength in the political vacuum that follows. At the end of the decade, Slovenia and Croatia become the first republics to slough off communism. Serbia remains under hard-liners.