When Nato troops first entered Kosovo in June 1999 after 78 days of bombing, no one thought its Kosovo Force (KFOR) peacekeepers would still be trying to separate ethnic Albanians and ethnic Serbs 24 years later.
The initial goal, as in Bosnia-Herzegovina, where another even smaller Nato force lingers, was for the Nato mission to withdraw as early as 2000, handing over administration to the United Nations and Kosovo's own authorities.
Instead, Nato is now sending an additional 700 troops, maybe more, to reinforce 4,000 already there.
This week's violence, in which more than 30 Hungarian and Italian Nato soldiers were injured in the town of Zvecan, appears to be the worst since the years following the war. The focus remains majority ethnic Serb settlements in the north of Kosovo, now emerging as a flashpoint at a time Nato and other Western allies have their minds on Russia's war in Ukraine.
Independence for ethnic Albanian-majority Kosovo came in 2008, almost a decade after a guerrilla uprising against Serbian rule. Serbia still considers Kosovo part of its territory and accuses Pristina of denying minority Serbs their rights.
Unrest intensified after April elections that were boycotted by ethnic Serbs, handing victory in four Serb-majority mayoral districts in the north to ethnic Albanian candidates.
Their installation last week, after a mere 3.5% voter turnout, drew criticism from the United States, which scrapped Pristina's participation in a Nato exercise as a result.
This week's violence broke out as Kosovan authorities, with accompanying Nato troops, took control of civic offices.
On Friday, the most involved Western nations in Kosovo -- the United States, France, Germany, Britain and Italy -- condemned Kosovo's decision to force access to municipal buildings despite calls for restraint. A joint statement also expressed concern over Serbia's decision to raise its military alert levels along the border.
Enthusiasm in the West for greater entanglement in Kosovo has rarely been lower. Some in the alliance have been quietly calling for years for the KFOR mission to be wound down. Others have worried its removal could prompt a complete unravelling of security, a concern that, if anything, has grown since the West's chaotic exit from Afghanistan in 2021.
Calls for the Kosovo authorities to de-escalate and all sides to avoid inflammatory rhetoric appear to have fallen on deaf ears. Within Kosovo itself, both the government and ethnic Albanian opposition parties say Western nations have no choice but to back the country they recognised as independent in 2008, although Russian, Chinese and Serbian opposition has prevented Kosovo's accession to the United Nations as a sovereign state.
Some Kosovo residents accuse both Vladimir Putin's Russia and the Serbian government of President Aleksandar Vucic of deliberately escalating tensions. Speaking on a visit to Kenya this week, Russian Foreign Minister Sergei Lavrov warned the situation could lead to a "huge explosion" at the heart of Europe, once again blaming Nato's 1999 intervention for creating the situation.
SIMULTANEOUS WAR CRIMES TRIAL
Mr Vucic said he spent the night with Serbian troops close to the border earlier this week, and his government continues to call for its forces to be allowed to enter Kosovo. Under the terms of the 1999 UN resolution that governs Nato's presence in the country, this would require Nato's agreement -- something it has so far refused.
Allowing Serb forces in would almost certainly exacerbate the situation and, at worst, risk open conflict -- with the United States also particularly outspoken in criticising the authorities in Pristina.
US Ambassador in Pristina Jeffrey Hovenier said the United States "foresaw the consequences" of the attempt to impose the ethnic Albanian mayors and had "strongly advised" Prime Minister Albin Kurti not to take such action.
In response, Washington said it was cancelling Kosovan participation in its major "Defender Europe 23" exercise run in coordination with Nato.
Under current circumstances, he said, the United States had "no enthusiasm" to assist Kosovo towards greater international recognition.
That, however, does not get Nato off the hook, particularly its KFOR mission, which has been commanded by Italy for most of the last decade in coordination with the EU and UN missions.
Clearly, commanders on the ground hoped their presence would mitigate against violence this week, but this was not the case in Zvecan, around 40 kilometres from Pristina. With Serb officials quitting the Kosovan police, Nato is in the unenviable position of having to support civilian authorities who appear increasingly divisive.
The confrontation also comes amid a wider muddying of the waters over Nato's original intervention. Former Kosovo president Hashim Thaci, a senior commander of the rebel Kosovan Liberation Army during the 1998-9 conflict, has just gone on trial for war crimes at The Hague, accused of at least partial responsibility for torture and killings at that time.
Western officials who served in Kosovo say the KLA was clearly implicated in multiple attacks on Serb civilians, although probably fewer than killings of Kosovo Albanians conducted by the Serbs. Western officials who served in Kosovo say it was never clear how powerful or involved Mr Thaci was.
In the short term, the Western and Nato priority will be to prevent further escalation, hoping that US and other pressure on the government in Pristina prompt it to pull back.
A worst-case scenario would see attacks on Serbs and more assaults against the Nato troops themselves.
For much of the first two years after the 1999 campaign, Nato forces struggled to keep angry Serb and Kosovo Albanian populations apart in the town of Mitrovica, the largest ethnic Serbian settlement in Kosovo and one where the writ of the Kosovo government barely runs on the north side of the bridge closest to Serbia.
That region saw particular tensions last year after the Kosovan government attempted to ban Serbian number plates within its borders, sparking occasional unrest that Kosovan officials said was further fuelled by social media disinformation blamed on Serbia and Russia.
The wider geopolitics are similarly complicated. Under Mr Vucic, Serbia has walked an awkward line between the West, China and the Kremlin -- for example, buying vaccines from all three during the Covid pandemic.
According to a classified Pentagon document released last month, Serbia had either already shipped some weaponry to Ukraine or was considering doing so, despite its protestations of neutrality and refusal to sanction Russia over its 2022 invasion. The government denied the allegation.
As Nato prepares for its annual summit in Vilnius in July, it will be hoping Kosovo has calmed down by then rather than risk it distracting a conference aimed primarily at building up defences against Russia.
Those in the Kremlin may be hoping for the opposite. Reuters
Peter Apps is a Reuters columnist writing on defence and security issues.