Arguably the biggest came in 2016, when Montenegro accused Russian military intelligence officers of orchestrating a coup attempt involving the pro-Serbian opposition and aimed at halting the country’s accession to NATO.

Moscow dismissed the allegations as anti-Russian paranoia, but in May this year, a Montenegrin court sentenced Russian military intelligence staffers Eduard Shishmakov and Vladimir Popov – in absentia – to 15 and 12 years in prison respectively.

The trial also found 11 other Serbs and Montenegrins, including two opposition leaders, guilty for plotting to commit “terrorist acts” and undermine the constitutional order of Montenegro.

The trouble started on October 16, 2016, as the country voted in a parliamentary election.

Police arrested a group of 20 people, including the former head of Serbia’s Gendarmerie, Bratislav Dikic, and the pro-Western government under Milo Djukanovic announced it had foiled an attempted Russian-backed coup.

The aim, it said, was to bring pro-Russian parties to power and prevent Montenegro from joining NATO, which the country eventually did so in June 2017.

Some observers still question whether the Kremlin was fully behind the alleged plot, pointing to a number of holes and discrepancies in the indictment, though a report by the US Foreign Policy Research Institute in July 2018 said Russia had been ready to go to “any lengths” to being down Djukanovic’s government in 2016.

Bulgaria charges pro-Russian leader with spying