SKOPJE, North Macedonia — Only two months ago, the leader of the small Balkan nation of North Macedonia was riding high, feted by world leaders, praised by the head of United Nations for offering a rare bright spot in an otherwise troubled global landscape and on the shortlist for a Nobel Peace Prize.
Prime Minister Zoran Zaev had staked his political career and his country’s future on resolving a three-decade-old dispute with neighboring Greece over his nation’s name. And through often tortuous diplomacy and against great odds, he had succeeded.
But as he sat outside his office in the capital city, Skopje, that all seemed far away.
“I am breaking inside,” he said.
The name change was expected to clear the way for talks on North Macedonia joining the European Union, but last month, France vetoed those discussions, arguing that the process of enlarging the bloc needs to be rethought.
That threw the government here into turmoil, and more ominously, it is shaking up the status quo in a region where an uneasy peace has existed since the bloody breakup of Yugoslavia in the 1990s and the wars that followed.
“That destroyed me personally, psychologically,” Mr. Zaev, who is stepping down as a consequence of the decision, said during a recent interview. And he was concerned not just about himself and his country, but for the stability of the entire western Balkans.
“Nationalism and radicalism can rise again,” he said. “There is a risk to open conflicts inside of the countries again. Also to open conflicts between countries again.”
Since the end of the Balkan wars in 2001, the deadliest conflict in Europe since World War II, integrating the former combatants into the European Union has been a central part of fulfilling the longstanding vision of a Europe whole, free and at peace.
But it has been an uneven path. Slovenia and Croatia are already in the union. Montenegro and Serbia are working on reforms required before membership. Albania and Northern Macedonia are just trying to start along the long path to accession.
The other two countries in the region — Kosovo, and Bosnia and Herzegovina — are not that far along, verging on failed states.
The goal of the enlargement process, its supporters say, is to provide the guideposts for better governance.
“We are led by the lights given to us by Europe,” Mr. Zaev said. “Now they turned out the lights and we are in the dark. Who knows where we go from here.”
European Union expansion into eastern Europe ties former Communist countries to the West, reducing Russian influence, but there are already signs that the undermining of Northern Macedonia is causing leaders in the region to reconsider their own positions.
Prime Minister Aleksandar Vucic of Serbia signed a free-trade agreement with a Russia-led economic bloc despite warnings from Brussels that the deal could jeopardize its membership bid.
“We need to take care of ourselves,” he told the Financial Times. “That’s the only way. That’s the only approach.”
Western diplomats expressed concern after Serbia conducted joint military exercises with Russia that featured the Russian S-400 and Pantsir-S anti-aircraft missile systems.
“We are talking about fantastic systems,” Mr. Vucic said after attending a computer-simulated drill near Belgrade. “If we had S-400, no one would dare overfly Serbia.”
He announced plans to buy the weapons, telling state television that he won’t allow Serbia to “be as weak as it was in the 1990s.”
Matthew Palmer, an American envoy for the Balkans, warned that Serbia could risk sanctions over the arms deals with Russia, with punishments ranging from visa bans to the denial of export licenses.
The competition with Russia has not stopped President Emmanuel Macron of France from delaying European Union expansion. His position no doubt has much to do with domestic politics, and his desire to keep anti-immigrant nationalists on the far right at bay.
But there is also recognition that some of the eastern European nations that are the bloc’s more recent members have been plagued by corruption, and have undermined competitive elections and independent media and judiciaries.
Even so, North Macedonia’s boosters are pressing Mr. Macron to reconsider. American diplomats, in particular, view the resolution of dispute between Northern Macedonia and Greece as a signature triumph of diplomacy.
At the Warsaw Security Forum this fall, Daniel Fried, a former United States ambassador to Poland and a member of the Atlantic Council, said that the name deal was “the best thing in the region in many years.”
“That is a big deal,” he said. “The Greeks stared down their own nationalist constituency and so did the Macedonia government.”
Speaking just days before Mr. Macron’s “non” on moving forward, Mr. Fried said that accession talks were now a “moral imperative.”
“The E.U. accession process provides a certain amount of leverage,” he explained. “I want to use that leverage. To not use it, to demonstrate that it was all some kind of moving of the goal posts, would be devastating.”
Though American and European diplomats are now scrambling to contain the fallout, it will prove difficult.
Bratislav Grubacic, the publisher of VIP news services in Belgrade, said that great damage had already been done.
It was no coincidence, he said, that Mr. Vucic will goto Moscow on Dec. 4 to meet with President Vladimir V. Putin.
“Russians used to say to Serbia, ‘You decide Kosovo, in whatever way you want, and we will support it,’ ” he said. “But it is clear now that Russia has other ideas. It seems these Russian arms are part of this bigger game.”
Even before the decision by France, there was growing concern about Russia taking a more aggressive posture in the region.
Those worries were heightened after an attempted coup in Montenegro in 2016 that Western intelligence officials say was directed by Russia to deter the country from joining NATO.
During an interview this summer, Srdjan Darmanovic, the foreign minister of Montenegro, said that stopping the expansion of NATO was not Russia’s only goal.
“I’ve often said that NATO is not Russia’s primary target, but the E.U., as a softer entity,” he said.
Unable to rely on the European Union, Mr. Vucic and other Balkan leaders have recently talked about building greater regional cooperation.
Mr. Grubacic was dismissive of the idea.
“Drug smuggling, criminals and corruption” all are endemic, he said. “If you make regional cooperation agreements, it will be a regional cooperation of gangsters.”
Albert Musliu, the head of the Association of Democratic Initiatives in Macedonia, said he cannot recall a moment this fraught since the end of the war.
“In the 20th century, we have gone through a lot of hell,” he said. “But it was a hell with a vision.”
Even when that vision was wrong and misguided, leaders could tell the people they were taking them somewhere. For the past two decades, that vision has been joining NATO and the European Union.
“Now we are without a vision,” Mr. Musliu said. “And when there is no vision, other options start to appear.”
And they can be dangerous.
Mr. Musliu worries that outside actors could easily stir up divisions in North Macedonia, where roughly a quarter of the people are ethnic Albanians.
Prime Minister Zaev expressed similar concerns, saying it was “dangerous for everybody.”
The regions history proves the point, he said — “Recent history, not centuries ago.”
Following the postponement of accession talks, he announced that his government would step down in January, to be replaced by a technocratic government until elections in April.
When asked why he decided to take such a dramatic step, he said he had no choice.
“If we don’t call for elections, nationalism will rise,” he said.
“I am terrified.”
Steven Erlanger contributed reporting from Brussels.