Elections in the Netherlands, France and Germany this year have brought much drama to the old Carolingian core, where Charlemagne founded his empire in the ninth century. This has always been the richest and most strongly institutionalised part of Europe. But should the European Union continue to weaken, the most profound repercussions will be felt farther east and south.

There, along the fault line of the Austrian Hapsburg and Ottoman Turkish empires, former Communist countries lack the sturdy middle-class base of core Europe, and in many cases are still distracted by ethnic and territorial disputes 25 years after the siege of Sarajevo. They depend on pro-European Union (EU) governments as never before.

In Ljubljana, the capital of Slovenia, officials and experts talk about a so-called phantom frontier that still exercises people’s imagination. This is the “Antemurale Christianitatis”, the “Bulwark of Christianity”, proclaimed in 1519 by Pope Leo X, in a reference to the Roman Catholic Slavs considered the front line against the Muslim Ottoman Empire. Croatia was the first line of defence and Slovenia the second. “When Yugoslavia collapsed, it was assumed that none of this earlier history was important,” one official said to me recently. “But a quarter-century after the disintegration of Tito’s Yugoslavia, we find that we are back to late-medieval and early-modern history.”

The Slovenes, governed for hundreds of years by the Austrian Hapsburgs, had in 2016 a per-capita income of $32,000 (Dh117,696). The Croats, with their mixed history of Austro-Hungarian, Ottoman and Venetian traditions, had a per-capita income of $22,400. But in the rest of the former Yugoslavia, which fell almost completely within the Ottoman Empire, Montenegro has a per-capita income of $17,000 and Serbia’s is $14,000. Macedonia, Kosovo and the former Ottoman parts of Bosnia register similarly low numbers.

This is not ethnic or racial determinism, since the Slavs of southeastern Europe have been shaped politically and economically more by the agency of foreign imperialism than by their own blood and language. The former Byzantine and Ottoman part of Europe is still the poorest, least stable and most in need of support from the EU. Whether Europe remains a secure and prosperous continent, or fractures along traditional east-west fault lines — with authoritarians in Russia and Turkey carving out zones of interest — will play out most vividly in the Balkans.

Russian President Vladimir Putin has been active throughout Central and Eastern Europe, and particularly in the Balkans, using various forms of subversion. Montenegro may be close to joining Nato, but it is often viewed as a veritable colony of Russian oligarchs and crime groups, where by some accounts Russia tried to stage a coup last year. Serbia and Bulgaria are seen as beachheads of Russian regional influence, even as neo-authoritarian governments farther north in Hungary and Poland bear growing similarities to the Russian regime. The effort by the Hungarian government to end the freedom of the Central European University, founded in Budapest by the Hungarian-American billionaire George Soros, has to be seen in this geopolitical context.

As for Turkey, President Recep Tayyip Erdogan won a referendum granting him near dictatorial powers last month. The next day, he visited the tomb not of Mustafa Kemal Ataturk, modern Turkey’s founder, but the tomb of Mehmed II, known as the Conqueror, the 15th-century Ottoman sultan whose imperial armies marched westward from Constantinople as far as Bosnia. Whether it is in Bulgaria, Macedonia or Kosovo, Erdogan is determined to fill the void opened by a declining EU.

Only if Serbia, Albania and Kosovo become members of the union can the ethnic dispute between Serbs and Albanians truly be solved. Within the EU, Albania and Kosovo will have no need of unifying on their own, an act that could become a casus belli for the Serbs. A similar dynamic holds for the contest between Croatia and Serbia for influence in Bosnia-Herzegovina. There is peace in the former Yugoslavia within the EU. There is only protracted conflict without it. The EU offers a system of legal states instead of ethnic nations, impersonal laws rather than fiat, protection for individuals over groups.

The EU, in other words, is the necessary empire.

I use the word “empire” advisedly. The EU has been such an ambitious enterprise mainly because it has sought a union over the former Carolingian, Prussian, Hapsburg, Byzantine and Ottoman domains, all with starkly different histories and development patterns. To accomplish that, the EU has had, in effect, to replace the functionality of those former empires. Even inside the open borders of the Schengen Area, within which EU citizens are guaranteed free movement, the union represents a sprawling territory, governed by a remote and only partly democratic bureaucracy, with many of its people demanding more direct representation. Isn’t this a form of late and declining empire?

So it must be saved — and improved. Jan Zielonka of St Antony’s College, Oxford, writes optimistically of a vibrant “neo-medievalism” in Europe: A dynamic overlapping of identities and sovereignties — supranational, national and local — as cities and regions vie with a revitalised EU for a claim on people’s loyalties. Unless there is a credible EU, the other layers of identity are not possible without conflict.

I recently visited the Croatian port city of Rijeka, close to the Slovenian and Italian borders, when the two-headed eagle was put back atop the bell tower. “It is a Hapsburg emblem, not a Croat, Hungarian or Italian one,” a local ethnic-Italian writer, Giacomo Scotti, explained to me. “It was taken down by the Fascists and symbolises the local freedom and autonomy that this city enjoyed under the Hapsburgs.” Mainly because Croatia is a sovereign state within the European Union, and working toward entry into the Schengen and euro zones, do the circumstances exist for such a nonthreatening display of local pride.

The great Italian scholar of Central Europe, Claudio Magris, refers to Tito in his epic travel book, Danube, as the last of the Hapsburg emperors, resembling Franz Joseph “because of his awareness of inheriting a supranational, Danubian legacy”. Like Franz Joseph, Tito held Yugoslavia together through a mixture of repression and, compared with other Communist states, benevolence. Now the states that were once part of Yugoslavia will find peace and security only through a far more benign imperial system: The EU. So what happens next in the core of Europe — whether, for instance, France joins Britain in seeking to exit the EU — is crucial to the rest of the Continent.

— New York Times News Service

Robert D. Kaplan, the author of Balkan Ghosts and In Europe’s Shadow, is a senior fellow at the Centre for a New American Security and a senior adviser at the Eurasia Group.