The devastating wars in the Balkans ended almost two decades ago but tensions have spiked throughout the region, where a battle for influence is playing out between Russia and the West.
Here are the key issues at stake:
- Montenegro's NATO accession -
Montenegro's veteran leader Milo Djukanovic has officially transferred power to his successor Dusko Markovic, but the goal remains the same: to join NATO this year.
The pro-Western path is, however, disputed -- and even triggered violent protests in 2015 in the small country of 620,000 people, who are predominantly Orthodox Slavs.
Djukanovic accused Moscow of being behind the anti-NATO rallies and the demands for a referendum on the issue.
Many fear that demonstrations could resume in the spring when parliament is expected to convene to ratify NATO accession, a move that Russia has deemed a "provocation".
In a dramatic twist, a group of Serbian nationals were arrested on the eve of Montenegro's October 16 election, accused of plotting a coup and the assassination of Djukanovic.
A Montenegro prosecutor has accused "Russian state bodies" of involvement in the conspiracy -- a claim strongly denied by Moscow -- and the suspects include two pro-Russian lawmakers, plus two Russians on the run.
- Bosnia's unity -
Having held a referendum last year on Bosnian Serbs' right to celebrate their own controversial "national holiday", their leader Milorad Dodik regularly talks about a vote on the secession of Bosnia's Serb-run entity, Republika Srpska.
Once a darling of the west, Dodik now laces his speeches with ultranationalist Serb rhetoric, appears with his ally Russian President Vladimir Putin and expresses fear over an alleged increase in Islamism among Bosnia's Muslims.
He is sceptical about the longevity of Bosnia, calling it "a place that nobody desires".
For Bosnian Muslims -- and the West -- a referendum on secession would be a red line in the deeply-divided country, coming more than 20 years after the inter-ethnic war that claimed 100,000 lives.
An expert in blowing hot and cold, Dodik assures that he will stay away from any "irrational" decision. "But we will not give up that idea," he insists.
- The Kosovo issue -
A former Serbian province and the scene of a 1998-1999 war that claimed 13,000 lives, Kosovo unilaterally proclaimed independence in 2008.
While its sovereignty is now recognised by more than 100 countries, Belgrade and its ally Moscow remain firmly against the move. The Serbian constitution includes Kosovo as its southern province.
Belgrade and Pristina have made tangible progress in improving ties in negotiations brokered by the European Union. A telecommunications deal, for example, allows Kosovo to have its own country code.
But in the last several months talks have stalled. Kosovo's ethnic Albanians, who make up around 90 percent of the population, are reluctant to allow an association giving greater autonomy to Kosovo's Serb minority, as agreed with Belgrade.
In January, Belgrade sent a propagandist train towards Kosovo, painted in the colours of the Serbian flag and bearing the message "Kosovo is Serbia" in multiple languages, sparking a war of words between political leaders.
The arrest in France of Kosovo's former rebel commander and ex-premier Ramush Haradinaj, on a Serbian arrest warrant for war crimes, has also strained ties.
- A new cold war? -
EU President Donald Tusk said this week that "tensions and divisions have got out of hand" in the Western Balkans, "partly due to unhealthy external influences which have been destabilising several countries for some time".
For Milos Solaja, a professor of international relations in the northern Bosnian town of Banja Luka, Russia is "strengthening its position" while NATO wants to "be as close as possible to Russian borders".
On a visit in January to Sarajevo, NATO chief Jens Stoltenberg said the alliance was "very closely" monitoring the "increased" influence of Russia in the Balkans.
But NATO remains the dominant regional force: Moscow can only count on the support of Serbs. Croatia, Albania, Bulgaria and Romania already belong to the western military bloc, and NATO-led troops have been deployed in Kosovo since the end of the war.
When Montenegro joins, NATO will cover the entire Adriatic coast. That "will bury Russia's dream, going back to tsarist era," of access to Mediterranean, says former Bosnian diplomat Hajrudin Somun.