Securing the peace is often as difficult as waging the war. While there are encouraging signs that NATO has won its campaign to stop the brutal mistreatment of the ethnic Albanians in Kosovo, a lasting peace cannot come to the Balkans unless all interested parties take steps to prevent new ethnic conflicts from erupting. Kosovo is not the only place where such a threat exists; as the only NATO country that has a border with Yugoslavia, perhaps no member of the alliance understands this threat better than Hungary does.

On the Yugoslav side of our common border, in the Serbian province of Vojvodina, nearly 350,000 ethnic Hungarians have been virtual hostages for the past several months--as both the Yugoslav authorities and some local Serbs have constantly reminded them. As a "NATO minority," these Hungarians are a defenseless and easy target for Serbian anger over the NATO bombing and the likely setback in Kosovo. Seeing the plight of Kosovar Albanians, the Hungarians and other non-Serbs living in the Vojvodina understandably fear that they might be the next victims. History provides justification for their worries.

Yugoslavia, cobbled together at the end of World War I, has always included a large variety of nationalities that spoke several languages, used two alphabets and adhered to various religious faiths. Its centralized government, dominated by Serbs, failed to win the loyalty of the citizens. The country's post-1945 Communist dictator, Tito, apparently learned from the mistakes of his predecessors and reconstructed Yugoslavia along federal lines. Sensitive to Serb national sentiment, he did not make Kosovo a separate republic, but instead granted it wide autonomy, a kind of home rule. A similar status was created in the north for the Vojvodina, which prior to 1918 was part of the 1,000-year-old kingdom of Hungary.

The Vojvodina suffered a kind of "ethnic cleansing" between 1456 and 1718, when it was a war zone in which Hungary fought the invading Ottoman Empire and most of the Hungarian population was killed or deported to be sold as slaves. Liberated from the Ottoman Turks, southern Hungary (today's Vojvodina) underwent a repopulation that made it the most colorful ethnic mosaic of Europe. In 1910, its 1.3 million inhabitants included 30.2 percent Hungarians, 25.2 percent Greek Orthodox Serbs, 23 percent Germans ("Swabians"), about 10 percent Roman Catholic South Slavs (Croats, Bunjevci) and the rest other nationalities (Slovaks, Romanians, Rusyns).

But 70 years of deliberate colonization drives, expulsions and even mass killings (in 1944, during World War II) significantly changed the Vojvodina's ethnic composition. By 1991 the proportion of Hungarians had been reduced to 16.9 percent, the Serb population had increased to 56.8 percent and the Germans had been completely "cleansed." In the past few years, another 250,000 Serbs (refugees from Croatia and Bosnia) were settled in the province and 50,000 Hungarians have left, making today's Serb percentage even greater.

It is unrealistic to expect the victims of war crimes and reprisals to live happily with the perpetrators of those crimes. But if the international community does not want to redraw borders and create ethnically homogeneous states through massive population transfers, it is necessary to find ways for the continued peaceful co-existence of the various ethnic communities. That can be achieved only by decentralization--giving extensive administrative self-government to smaller units having a special geographic, ethnic and economic character, based on the Swiss model of national cantons.

Hungarian Prime Minister Victor Orban pointed out during the recent NATO summit in Washington that NATO's military intervention in Kosovo was meant to prevent the conflict from spreading further. So if and when military actions stop, a Balkans conference should be convened to discuss the widest possible range of regional issues, including the security of the Vojvodina.

We in Hungary are confident that the Vojvodina will not become the next scene of mass violence. Serbia has a strong interest to remain on speaking terms with Hungary, its window to the outside world, through which essential lines of communication and access routes run. But there is also a very real danger that, if and when a settlement is reached over Kosovo, the multiethnic Vojvodina may be forgotten--just as no one thought about Kosovo when the Dayton accord ended the hostilities in Bosnia.

What are the ironclad guarantees needed in the Vojvodina? All non-Serbs, as well as many Serbs who live in that province, want the restoration of the autonomy that was abolished 10 years ago along with Kosovo's. Under a system of cultural autonomy, non-Serbs would regain the right to use their native language and alphabet in public life, as well as in schools and institutions of higher education. Most importantly, if these measures are to remain more than empty promises, the non-Serbs need guarantees in the form of an international presence, such as an observer mission from the Organization for Security and Cooperation in Europe. With such a presence, the tragedies of Bosnia and Kosovo might have been avoided.

After the war in Croatia eight years ago, when I was Hungary's foreign minister, I offered suggestions about how to address some of the problems in the Balkans. In one of my letters, dated Dec. 8, 1991, I made the following appeal to the European Community and to Cyrus Vance, then representing the secretary-general of the United Nations: "The U.N. should immediately try to send peacekeeping forces not only to the territory of Croatia but also to those areas of Yugoslavia where there is still a fragile peace: to Bosnia and to the two formerly autonomous provinces, Vojvodina and Kosovo. Without that, a wholesale massacre may occur."

As of now, even with the Yugoslav parliament's vote to accept NATO's conditions for ending the bombing, we are far from discussing the best post-war legal arrangements for the Balkans. Hungary, although one of NATO's newest members, has proved a loyal ally in NATO's fight. Twenty-four F-18 Hornets have been flying sorties from the Taszar air base in southern Hungary, and a number of tankers have been deployed at Budapest's civilian airport. We sent a medical team and military personnel to help the refugees in Albania. We have done all this because we are fully aware of the dangers represented by the policies of the present Belgrade government.

But a democratic Yugoslavia is not a distant dream. By complying with the demands of the international community, the Serbs can ensure that peace can return to the entire country and that reconstruction can start immediately. Both the European Union and the United States have outlined plans for the economic stabilization of southeastern Europe, from the Black Sea to the Adriatic. Serbian democrats in Montenegro, in the Vojvodina, in exile and also in Belgrade are eager to rejoin a cooperative Europe and to help heal the wounds. Let us hope all Serbs recognize that the door is open, and walk through.

Geza Jeszenszky is the Hungarian ambassador to the United States. A historian, he was the country's minister for foreign affairs from 1990 to 1994.