Serbia's neighbors are no strangers to the red, blue, and white tricolor flags that fly outside some homes and Serb-led institutions or are splashed around some of the ethnically charged political rallies in the region.
After all, there are a combined 1.3 million ethnic Serbs in Bosnia-Herzegovina, Montenegro, and Kosovo alone, according to estimates.
But all three of those countries are likely to see increased flag-waving and other public expressions of Serbian identity this week on a joint holiday declared last year by the governments of Serbia and of Republika Srpska -- the mostly Serb entity that along with the Muslim and Croat federation composes Bosnia-Herzegovina.
"I support the day and I think it benefits everyone, especially students, because it shows us that we should be united, to respect our compatriots in all countries," says Rastko, a high school senior in Banja Luka, Republika Srpska's capital.
He cites historical themes that are "common to all of us nationally," such as his school's plans to teach a lesson on the Salonica Front, also known as the Macedonian Front.
That World War I theater of battle's liberation in 1918 is ostensibly why Belgrade and the secession-minded leadership of Banja Luka decided -- in lightning succession over two days last year -- to celebrate Serbian Unity, Freedom, and National Flag Day every year on September 15.
But the shared heritage of a century-old battle attributed to Serbian forces and a cross-border celebration of Serbian nationality -- in a region freshly scarred by ethnic warfare -- is less self-evident to some of Republika Srpska's non-Serbs.
To me, it's this effort to try to emphasize nation-building beyond the borders of the state of Serbia."-- Florian Bieber, Center of Southeast European Studies
Bosnia is still divided -- some would say dysfunctionally so -- by the parallel governing structures established along Bosniak, Serbian, and Croatian ethnic lines by the Dayton agreement 25 years ago to end three years of intense conflict accompanying the breakup of Yugoslavia.
Students in Srebrenica, the scene in Republika Srpska of one of postwar Europe's worst atrocities when Bosnian Serb troops massacred more than 8,000 Bosniak men and boys in 1995, complain that while Serbs should be allowed to celebrate their heritage, republican officials avoid events more closely aligned with Bosniak or Croat identity and history.
One student, Alija, calls Serbian unity day an official effort at "segregation, discrimination, and humiliation of non-Serbs in Republika Srpska."
Meanwhile, analysts warn that the holiday looks like a politically cynical and wrongheaded effort radiating from Belgrade to emphasize nation-building beyond recognized borders while encouraging the notion that Serbian national identity is under threat.
Such a campaign has rattled neighboring governments and could threaten the current Serbian leadership's preferred narrative of their country as a regional political and economic leader, analysts say.
"To me, it's this effort to try to emphasize nation-building beyond the borders of the state of Serbia," Florian Bieber, director of the Center of Southeast European Studies at the University of Graz, says of the new Serbian holiday.
He calls it a "symbolic manifestation" of Serbia's long-standing reluctance to accept its borders after the dissolution of Yugoslavia in the 1990s.
It also hints at political opportunism as hopes of an early EU entry fade and a "natural inclination" of Serbian President Aleksandar Vucic toward his political and ideological origins "in Serb nationalism and an anti-Western worldview," according to Bieber.
And all of it amid intensifying talk in Belgrade of a new "Serbian world" that critics say is little more than a new label for ethno-nationalist ambitions of a "Greater Serbia."
"The basic issue, if you're a nationalist, is how to conceive of this relation between the people inside the state and the people outside the state," says Eric Gordy*, a professor at University College London's School of Slavonic and East European Studies. "And that's what they've been talking about for 100 years."
The "big political dilemma" in Serbia -- where frustration particularly among young people has fed a demographic crisis that has reduced the population to under 7 million -- is that a large number of Serbs don't live there, Gordy says.
I have never said, and I won't react more harshly because if [Interior Minister Aleksandar Vulin] hadn't said 'Serbian world,' you would have invented something else just so that Serbs would be guilty of something."-- Serbian President Aleksandar Vucic
That fosters European fears of a return to the kind of conflict that wracked the region in the 1990s, killing at least 130,000 people and displacing millions more.
Gordy and consistent polling suggest there's no appetite for more war in the Balkans.
But like Russia in the 19th century with its appeals to pan-Slavism and Hungarian leaders' ongoing posturing as the protector of ethnic Hungarians abroad, Serbia looks like it's "attempting to achieve what they tried to achieve through force [in the 1990s] but in a softer way," Gordy says.
In that sense, he says, the new Serbian unity holiday looks like projecting influence while "promoting this idea that the national identity is threatened."
Serbian Unity, Freedom, and National Flag Day is a collaborative project between Belgrade and Banja Luka.
It was first organized last September by current Bosnian Serb leader Milorad Dodik, one of three members of the Bosnian presidency and an avowed separatist who, in the words of the director of the Center for Regionalism in northern Serbia, "spends more time in Belgrade than in Banja Luka."
There was no need to reconcile it nationally in Bosnia since the country has no unified law on public holidays.
A day later, after Vucic noted that it broke no laws, the Serbian government followed suit, and the joint holiday was born.
Within a week, public buildings and major institutions in both Serbia and Republika Srpska were festooned with Serbian flags as ceremonies were held and anthems broadcast to mark the holiday.
Always 'Guilty Of Something'
This year, Serbian unity day arrives with several of the region's governments on guard against interference from Belgrade.
EU enlargement has lost its sizzle on both sides, disappointing a handful of Western Balkan states and eroding one of the prime incentives for lasting democratic and institutional reforms in the region.
Censuses have been postponed in Serbia, Montenegro, Kosovo, and North Macedonia, in part, over obstacles to the accurate enumeration of ethnic minorities. (Bosnia isn't due for a new census until 2023.)
The internationally mediated Serbia-Kosovo normalization effort remains largely stalled, with a more politically pugnacious Kosovar prime minister, Albin Kurti, in charge of negotiations for Pristina.
And tensions have even mounted between Belgrade and Podgorica, the capital of neighboring NATO member Montenegro, where around one-third of citizens identify as "Serb." Scuffles broke out there last week over Serbian influence and the enthronement of the Serbian Orthodox Church's top local cleric in a former Montenegrin capital.
Vucic was forced to publicly distance his administration from the notion that it was pursuing a "Serbian world" that threatened Montenegrin or Bosnian independence.
"As for the 'Serbian world,' that is a phrase used by [Interior Minister Aleksandar] Vulin and it is not part of the official policy of the state of Serbia," Vucic said at a press conference.
"I have never said that," Vucic said, "and I won't react more harshly because if he hadn't said 'Serbian world,' you would have invented something else just so that Serbs would be guilty of something."
What's A 'Serbian World' Anyway?
"Serbian world" is a term coined -- or at least popularized -- by right-wing Serbian historian Aleksandar Rakovic a little more than a year ago.
In a front-page polemical in the Balkans' oldest surviving newspaper, Politika, in July 2020, Rakovic suggested that a "Serbian world" exists that implies the unification of Serbia, Republika Srpska, and Montenegro.
The term was quickly adopted by Interior Minister Vulin, a veteran Serbian nationalist politician and member of the cabinet whose Socialist Movement has governed alongside Vucic's senior Progressive Party (SNS) since 2012.
Vulin acknowledged that current circumstances didn't allow for the creation of a single state to unite all Serbs, but he predicted it would happen within decades.
"There was no talk of the 'Serbian world' five years ago, or anything of that sort," says Bieber.
He calls its public emergence part of a "continuous" effort, but one that has escalated in recent months.
"It's gradual and incremental, but it's certainly a distinctive shift away from where Serbia positioned itself [previously], and it's got a lot to do with the fact that EU integration is just not that powerful [of an incentive] anymore," Bieber says.
Until last week, Vucic had mostly batted away questions about a "Serbian world" policy, despite explicit calls by Bosnian Foreign Minister Bisera Turkovic and Kosovar President Vjosa Osmani for him to reject it.
And Jeta Krasniqi, project director at the Kosovo Democratic Institute in Pristina, an NGO, tells RFE/RL that the ethno-nationalist tones mean that "any kind of project of this kind needs to be taken seriously."
She notes that despite the Serbian president distancing himself from talk of a "Serbian world," Vulin remains a key minister with a decade of experience working in tandem with Vucic.
Krasniqi, who participated in a meeting between regional leaders and outgoing German Chancellor Angela Merkel during the latter's farewell tour of the Balkans on September 14, says that despite the cooling of accession efforts, "it is up to the EU to reject this kind of rhetoric."
Enough Is Enough
But absent the carrot of EU membership in the immediate future, will Belgrade listen?
Gordy warns that the Serbs' recent use of the term "Serbian world" is "part of that continuum" that includes visions of a Greater Serbia or would-be efforts to create a "sphere of influence" in the Balkans.
He speculates that Serbian public opinion is probably "broadly sympathetic" to the idea of a "Serbian world," and that if Vucic thought he could succeed at promoting it he might be "behind it all the way." And sometimes, he warns, "unfortunately the only thing that really stops these kinds of campaigns is failure."
But Gordy predicts that outside pressure will only mount on Vucic to cool his language and notes the challenges for a country like Serbia.
"What makes it difficult here is that this [creation of spheres of influence] is something that major powers can do because they're major powers. Serbia is not a major power, so it's not going to be able to enforce that claim in the same way.
"I think he's seeing it backfiring and stepping away from it," Gordy says of Vucic.
Bieber says it's a "worsening problem" that's "becoming more and more pertinent and stronger in recent months."
But the stakes for Vucic and Belgrade are particularly high, he says, given their efforts to paint Serbia as a regional power in the rapidly changing Balkans.
So the crucial question is how Serbia decides to resolve the "continuous tension" between policies that promote good relations with its neighbors or ones that favor an ethno-nationalist policy toward ethnic kin.
"Being able to get away with more, in a certain way, and having [neighboring] countries which have weaknesses -- like Kosovo sovereignty, Bosnia's fragmented nature of politics, and in Montenegro the [deep] political divisions -- all of these things make it easier for Serbia to promote this kind of [ethno-nationalist] policy," says Bieber.
"But that's something which again contradicts the other narrative of Serbia as a kind of leader of the region, not in an ethnic way, but in an economic and political way beyond supporting Serbs."