WARSAW—At 1 a.m. on the night of Feb. 4, CCTV cameras in the western Ukrainian town of Uzhhorod captured an unusual scene. Two unknown men were trying set a building on fire. They initially failed, but did not give up. Three hours later they came back to the scene—this time equipped with more gasoline—and threw a Molotov. This time it worked. The facade caught fire, and the strangers departed immediately, crossing the nearby border into Slovakia.

The fire was extinguished and caused only minor damage. But as it turned out, it was not an ordinary instance of small-town arson. The suspected culprits were two Polish citizens, both members of Falanga, a small, radical organization with fascist roots. On Wednesday they were arrested by the Polis Internal Security Agency (ABW) in connection with the arson. The building they targeted housed the Hungarian Cultural Society of Zakarpattia, one of the central institutions for the local 150,000-strong community of ethnic Hungarians living in the region.

Why would Polish far-righters attack Hungarians—and in Ukraine at that? After all, the two nations have for centuries considered each other best allies, and nobody is more keen to stress this “everlasting friendship” than nationalists from both countries.

The answer, in all likelihood, lies in the group’s ties to Russia. Members of Falanga have traveled to Donbas, the embattled east of Ukraine, to support —and, as some allege, fight for—the Russian-backed separatists there. The organization and its media arm, Xportal.pl, also have documented links to a marginal Polish pro-Russian political party “Zmiana” (Change), whose leader, former Member of Parliament Mateusz Piskorski, is in jail on suspicion of espionage for Russia.

“They seem like typical fodder for such operations. It’s the type of thing I would see back in my old days,” says one former Western counterintelligence official.

The incident in Uzhhorod, experts and officials suggest, was a small part of a much wider Russian campaign bent on fomenting ethnic tensions within Ukraine, with the goal of destabilizing the country and antagonizing its NATO-affiliated neighbors, especially Poland and Hungary. And it seems to be working.

“It’s an organized, coordinated Russian campaign, carried out by paid provocateurs as part of a broad information operation. It’s been directed to audiences in Ukraine, Poland, and Russia, and synchronized with the messaging of Russian state media” says Adam Lelonek, director of Center for Propaganda and Disinformation Analysis, a Warsaw based think tank. “There’s no doubt it has had a concrete effect, and has added fuel to the ongoing Polish-Ukrainian diplomatic feud.”

“ Why would Polish far-righters attack Hungarians—and in Ukraine at that? The answer, in all likelihood, lies in the group’s ties to Russia. ”

The campaign has consisted of a series of mostly small-scale cases of vandalism, arson, bombings, and fake demonstrations. Indeed, the arson in Uzhhorod wasn’t even the last such incident. The Hungarian center was again set on fire on Tuesday, this time causing some real damage.

The most serious of these provocations took place last spring in Lutsk, the regional capital of Volyn, a western Ukrainian region bordering Poland and Belarus. On the night of March 29 an unknown perpetrator fired several rocket propelled grenades at the Polish consulate.

But most others were of a somewhat lesser caliber: repeated vandalizations of cemeteries and monuments sacred to the Polish minority in Lvov and Volyn oblasts (as well as Ukrainian ones in Poland), Hungarians in Zakarpattia, and Bulgarians in Odessa; half-serious proclamations of separatist states like the “Rivne People’s Republic,” and obviously fake marches in the name of Ukraine’s Poles and Bulgarians demanding autonomy.

The perpetrators of most of the incidents were identified as members of another obscure, fringe movement—this one a Ukrainian group called Nazhdak—with links to Russia. After several months of inquiry, some of Nazhdak’s operatives were charged and sentenced, but its leader, Mykola Dulsky (who claims Polish ancestry) is said to have fled to Moscow.

According to Ukrainian authorities, Dulsky is in fact just a middle man, and the campaign was orchestrated by the so-called Ukraine Salvation Committee, based in Moscow, headed by fugitive former Ukraine Prime Minister Mykola Azarov, who fled to Russia after the government of President Viktor Yanukovych was deposed by the Maidan protesters in 2014.

“What they’re really implying is that the real force behind it are the Russian intelligence services, which is likely,” says Robert Cheda, a former Polish intelligence officer and an analyst at the Pulaski Foundation in Warsaw. “It is no secret that the nationalist milieux are heavily infiltrated by Russians. And the chances that Azarov and his group are not in some way connected with the services are close to nil.”

Cheda and other experts say that even though most of the provocations and plots seemed amateurish and fake, the steady, systematic “drip, drip, drip” campaign has had its effect on the relations between neighbors and within Ukraine.

“It’s taken its toll for sure. On Ukraine, Poland, Hungary—everywhere,” says Dmytro Borysov, a Ukrainian journalist based in Lviv, Ukraine, who has covered the incidents extensively.

“These incidents resonate outside Ukraine. And even if the authorities catch or identify the criminals, not everyone trusts the Ukrainian police or Security Service (SBU). Meanwhile the Ukrainian public and the national media are interested more in bigger topics, which means they don’t follow the investigations or raise awareness of the issue.”

“The problem is that it is easy to undermine official Ukrainian findings, given the sketchy reputation of SBU and the state apparatus,” Cheda points out. “And indeed you could come up with several possible alternative explanations—for example, that it is part of the war between oligarchs, or the nationalists, who are politically on the rise. But the truth is no matter who is behind it, Russia reaps the benefit.”

“ As with Russia’s influence campaign in the U.S., which was aimed at exploiting political and racial divisions, Moscow’s agents worked to inflame and exacerbate the existing tensions and cleavages. ”

Much as with Russia’s influence campaign in the United States, which was aimed at exploiting political and racial divisions, Moscow’s agents worked to inflame and exacerbate the existing tensions and cleavages. In Ukraine and Poland’s case, the most has been the history of the two nations.

Ever since Ukraine gained its independence in 1991, Poland has been a steadfast ally and Kiev’s chief advocate in its ambition of joining the Western institutions like the EU and NATO. But beneath the surface of exemplary diplomatic relations there long has simmered a deep-rooted dispute over the interpretation of history. Much of it is centered on the Volyn massacre, a wide-scale campaign of ethnic cleansing carried out by Ukrainian nationalists against the region’s tens of thousands of Poles during the latter stages of World War II. Poland officially considers the crime a genocide, but in Ukraine, where the perpetrators of it, the Ukrainian Insurgent Army (UPA) are hailed as heroes, the question is often ignored, minimized or justified by some officials. On the other hand, Polish officials are sometimes similarly dismissive of crimes committed by Poles, like punitive campaign against Ukrainians or, “Operation Vistula,” a forced resettlement of over 100,000 ethnic Ukrainians.

These resentments, up until now largely brushed aside, are now a major sticking point in the neighborly relations, which are deteriorating quickly.

Even though officials from both countries have suggested Russia is trying to spoil things between them, Warsaw’s and Kiev’s policies haven’t exactly helped to avoid that. Quite the contrary.

The destruction of a Polish memorial in Huta Pieniacka, dedicated to victims of a massacre perpetrated by Ukrainian Nazi collaborators from SS Galizien, has inflamed a conflict—continuing to this day—over which monuments should be rebuilt and which ones are lawful.

But a lot of the other problems were entirely self-created by governments exploiting nationalist narratives to score political points at home.

In February, Jarosław Kaczyński, the chairman of Poland’s ruling populist Law and Justice Party—and de facto ruler of the country—warned Ukraine that unless it faces its own history and resolves the dispute, its Western aspirations are in peril.

“ Most recently, Warsaw has angered Kiev by passing the so-called Holocaust bill. ”

Kaczyński proclaimed in an interview with a pro-government weekly, Gazeta Polska, that he had told Ukrainian President Petro Poroshenko that Ukraine would not enter the European Union as long as it brought with it veneration for Stepan Bandera and the Ukraine Insurgent Army (UPA). “You have to choose: either it’s integration with the West and rejection of UPA traditions, or it’s the East and everything that comes with it,” Kaczyński said.

This was followed by an even more explicit declaration from the then foreign minister, Witold Waszczykowski, who said Poland will block Ukraine’s European aspirations if it doesn’t change its stance on history. Waszczykowski then blacklisted “anti-Polish” Ukrainian officials and historians.

Most recently, Warsaw has angered Kiev by passing the so-called Holocaust bill. The act stipulates that anyone who denies or whitewashes any crimes committed by Ukrainian nationalists between 1925 and 1950 is liable to be sentenced to 3 years in prison. This is the same bill that made headlines when it criminalized any description of Auschwitz and other Nazi death camps as “Polish.”

Unsurprisingly, the Ukrainian element in this controversial law was included at the insistence of nationalist MPs from Kukiz’15 party after consultation with historians who allegedly have pro-Russian sympathies.

This has only helped to bait the Ukrainian nationalists—previously more concentrated on their enmity toward Russia—and encourages them to turn against the Poles.

“Here in Lviv the nationalist circles are now talking more and more about the ‘Polish spring’ scenario. They also fell victims to false narratives, fueled by Russian fake news, of separatist designs harbored by Poles,” says Borysov. “They even go so far as to accuse the city’s mayor, Andriy Sadovyi, of Polish separatism—a claim that originated with Russian fake news. These are still largely forces from the political fringe, but they’re not irrelevant.”

“ For Russia this is a perfect environment. ” — Robert Cheda, a former Polish intelligence officer

What’s more, the nationalists themselves—this time unprompted by Russia —have begun causing trouble. On Monday in Yavoriv, a small town near the Polish border, they destroyed a plaque dedicated to Polish King John III Sobieski. In its place they left a banner glorifying Stepan Bandera. A day earlier a group of them interrupted a ceremony in honor of Poles murdered in Huta Pieniacka.

But Artur Grossman, a Polish tour guide living in Lviv, says the worries are overblown.

“Poland is still well liked by Ukrainians, and considered by Ukrainians here a model country. The polls show only a marginal drop in that regard. Ordinary people don’t care about history. It only concerns a handful of journalists and politicians,” he says.

Still, the political feud shows no signs of stopping. And Ukraine, for its part, hasn’t avoided diplomatic blunders either. In July 2017, Kiev’s city council named one of the city’s avenues after Roman Shukhevych, the UPA commander responsible for the Volyn massacre. Later, the Ukrainian authorities obstructed the research of Polish historians in Ukraine, and in September, the Ukrainian Parliament passed a highly controversial education bill, which substantially restricted the ethnic minorities’ rights to study their national language.

That last measure has put Ukraine into a serious diplomatic crisis with Hungary. Its government—possibly the most Putin-friendly among EU member states—swore that the consequences will be painful for Ukraine and suggested it will stand in the way of the country’s integration with the West.

The recent attacks in Uzhhorod only made the crisis worse. In the wake of it, Hungarian Foreign Minister Peter Szijjartó summoned the Ukrainian ambassador to issue a sharp rebuke over growing “extremist tendencies” and the alleged intimidation of diaspora leaders. He also appealed to the European Union to defend Zakarpattia’s Hungarian minority.

“It’s sheer propaganda, and the claim of intimidation is exaggerated. Everybody knows these are Russian-initiated provocations, yet the Hungarian government never acknowledged it,” says Janos Szeky, a Hungarian journalist at Elet es Irodalom, a political weekly. “They say these are the results of a centrally directed anti-Hungarian hate campaign. Which is a vicious lie.”

“Basically, what we’re seeing in these spats is a clash of populist, assertive governments who consider themselves to be regional powers, and who pander to nationalist sentiments,” concludes former intelligence officer Robert Cheda. “For Russia this is a perfect environment.”