ZVECAN, Kosovo — In the densely forested mountains along the contested frontier between Serbia and Kosovo, a patrol of American soldiers under NATO command trudged through snow and mud, keeping an eye out for smugglers or anyone else trying to cross the border. Given the bloody legacy of this area, the situation is quiet now, at least up here.
It is down below, in Serbia and Kosovo, where old angers are resurfacing as the Balkan region that spawned so much suffering over the last century is again becoming dangerously restive. And once again, Russia is stoking tensions, as it seeks to exploit political fissures in an area that was once viewed as a triumph of muscular American diplomacy — but that now underscores the growing challenges facing NATO and the European Union.
“Russia sees the West meddling in its backyard, and President Vladimir V. Putin wants to show he can reciprocate,” said Dimitar Bechev, an expert on Russia and the Balkans and head of the European Policy Institute in Sofia, Bulgaria. “They see the Balkans as the West’s underbelly, and they use it to throw their weight around and project power on the cheap.”
Nearly 18 years after a United States-led intervention ended Serb domination of Kosovo, the border patrols are part of the longest-running mission in NATO history. Even as the European Union has made limited progress in brokering a political settlement between Kosovo and Serbia, the presence of NATO forces has maintained an uneasy peace, with animosity between the minority Serbs and majority Albanian inhabitants of Kosovo still palpable.
Yet NATO is now confronting its own challenges, whether it is the seeming ambivalence of President Trump toward the alliance or an increasingly provocative Russia. The alliance has sent reinforcements to Poland and the Baltic States to counter Russian actions, but Russian involvement in the Balkans has gotten less attention.
Russia has deep historical ties with Serbia and vehemently opposed NATO’s war over Kosovo in 1999. After an American-led bombing campaign, Serbia lost control over the region but continues to support Serbs there, vowing never to recognize the sovereignty of Kosovo, which it considers the cradle of the Serbian nation and of its Christian Orthodox faith. Mr. Putin has continued to back Serbia, as well as Serbs living in Bosnia and Herzegovina — and continued to dabble in the complex swirl of Balkan politics.
For starters, Moscow supported Bosnian Serbs when they held a controversial referendum in November that could lead to more — or even full — independence from Sarajevo. A month later, Russia backed fringe opposition parties in delicate national elections in Macedonia, another former Yugoslav republic. The European Union had organized the election to help bring the country back from the brink of collapse.
In Montenegro, Serbia’s tiny neighbor and a former Russian ally now set to join NATO, the authorities said they had foiled an October coup attempt that had been orchestrated by the Russians.
Then in January, Moscow moved to help Serbia undermine Kosovo’s independence by supporting a series of provocations that have damaged diplomatic normalization efforts, known as the Brussels dialogue, that are sponsored by the European Union. That process had recently produced a small breakthrough, as Kosovo was about to get its own +383 calling code.
Since Kosovo declared independence in 2008, however, the ethnic Albanian-dominated government in the capital, Pristina, has failed to bring the predominantly Serb parts of the country north of the Ibar River under its control, including Mitrovica, Kosovo’s second-largest city.
But as Kosovars were celebrating this breakthrough, the Serbs erected a concrete wall separating the northern, predominantly Serb part of Mitrovica from the ethnic Albanians in the southern part. It was built on the Serbian side of the bridge that crosses the Ibar, a project that the European Union funded in hopes of linking the divided communities.
European Union officials furiously demanded that the wall come down, but the Serbs remained defiant, forcing the official inauguration of the bridge to be postponed. This month, concrete blocks of the wall were bulldozed, but a metal barrier is still standing, blocking traffic and pedestrians.
Most inflammatory, the Serbian government sent a Russian-made train from Belgrade to Mitrovica, adorning its coaches with signs declaring that “Kosovo is Serbia” in more than 20 languages. Kosovo stopped the train at the border, accusing Serbia of wanting to stage an invasion of northern Kosovo, modeled on Russia’s annexation of Crimea. Serbia, in turn, accused ethnic Albanians of laying mines along the railway tracks and planning a bombing campaign of Serbs and their holy sites.
Serbia’s president, Tomislav Nikolic, who is thought to be backed by Russia as he seeks a second five-year term in the April election, threatened to send his troops back to Kosovo to protect the Serbs, if necessary.
“If Serbs are killed, we’ll send the army to Kosovo,” Mr. Nikolic said after the train episode, which was ostensibly intended to restore a line that had been disconnected since the 1999 NATO bombing of the area. He warned officials in Pristina against attempting to provoke a conflict, saying it would “end badly.”
Russia’s ambassador to Serbia, Aleksandr Chepurin, wrote in a recent editorial in Serbia’s daily Politika that Moscow would support “Serbia in preventing attempts to create an artificial pseudo-state of Kosovo.”
Milan Nic, a Balkan analyst at the GlobSec Policy Institute, a think tank in Bratislava, Slovakia, said that tough statements on Kosovo were common during Serbian elections but that Serbia could never improve relations with the European Union, let alone join it, by clinging to its former southern province.
Col. Corwin Lusk, the American commander of NATO’s multinational battle group in eastern Kosovo, agreed that the Serbian elections were fueling the angrier statements and that Russia was playing games, though he was skeptical that Moscow wanted a direct confrontation in the Balkans.
“It would be very irrational behavior because it’s a fight they could not win,” he said. “It’s a fight nobody would walk away from without scars and bruises.”
Many ethnic Albanians and Serbs living in Kosovo fear another round of war. Roughly 120,000 Serbs live in northern Kosovo, near the Serbian border, and mostly embrace the nationalistic fervour of Belgrade. But there are 70,000 other Serbs scattered in southern Kosovo who feel more exposed to retaliation.
In the town of Decani, in southwest Kosovo, 20 Serbian monks are holed up a 14th-century Serbian Orthodox monastery, which is recognized as a Unesco world heritage site and is being protected by NATO troops to prevent assaults from non-Serbs. The abbot of the monastery, Father Sava Janjic, said the nationalistic talk from Serbia “often comes back to us like a boomerang.”
“Every time they call me from Serbia, they ask: ‘Is there war? Are they trying to kill you?’’’ said Father Janjic, 52. “I tell them, ‘No, they are not.’ There is no war. I can’t lie. But the situation is far from rosy.”
NATO’s task in the region is deeply complex. Troop levels have dropped to about 5,000 over the past decade, including 650 American soldiers, and their job includes border patrols as well as navigating the sensitivities of an ethnically divided region.
In the absence of an army of their own, most ethnic Albanians see NATO troops as protectors of their state in Kosovo.
“They are here to defend us from the Serbs when they want to storm back,” said Belkiza Sahatqiu, 46, a mother of three, who works in a shoe store in the Serbian-part of Mitrovica.
Many Serbs living in Kosovo, however, describe the alliance’s forces as occupiers more than protectors, said Lilijana Milic, who owns a farm along the highway between Mitrovica and Pristina.
“They are not protecting anybody, certainly not us,” she said. “They came to occupy this land, and now they sit in their bases. Where were they when people were chased out of their homes in broad daylight?”
At the same time, Ms. Milic blamed Serbian politicians in Belgrade for the misfortune of Kosovo’s Serbs. “They just talk, talk, talk, talk about defending us,” she said, “but all they ever do is take care of their own interests.”