The Balkans are the main source of mercenary fighters for Russia, according to the National Resistance Center, an organization operated by Ukraine's Special Forces.
According to the center, a key figure in the recruitment process is veteran Serbian mercenary sniper, Deyan Berich, who fought for Russia against Ukraine in 2014. Another important Serb mercenary was identified as Zika Radoic, who is currently fighting for Russia.
Russia is increasingly relying on mercenaries in Ukraine, according to British government officials, who said that there are now 20,000 Wagner Group fighters in the country.
Wagner Group is a Russian state-controlled paramilitary formation that is primarily fighting in the area of Bakhmut, the site of the heaviest hostilities along the entire front line.