Since Russia's invasion of Ukraine, a lot has been made of the involvement of the Wagner Group – a mercenary group tied closely to Russia's military.
It is not just in Ukraine that the group has been present alongside Russian troops; Wagner Group members have appeared in Syria and a number of African countries.
The group has been accused of war crimes and abusing human rights.
However, the Commons Foreign Affairs Committee recently heard how nearly 8,000 mercenaries from the Wagner Group had been deployed in Ukraine by Russia.
The committee also heard how 3,000 members of the group were also thought to have been killed on the battlefield.
But what is the group and how does it operate alongside the Russian military in Ukraine?
Defence expert Professor Michael Clarke, a former director of the Royal United Services Institute (RUSI), the defence and security think tank, told Forces News the group, alongside the Chechens, is one of the only groups "who are flexible, can operate in small units and are quite agile".
Watch: Mozart Group – the counter to Russia's infamous Wagner Group mercenaries.
"On the other hand, they're not really integrated into the whole system, they're not part of the armour or artillery or airborne forces," he said.
This week, the Ministry of Defence tweeted Wagner was now "hiring convicts and formerly blacklisted individuals" as it continued to suffer casualties – with the group's value to Russia reducing as casualties continue.
Andrew Milburn is a former US Special Operations Colonel and now member of the Mozart Group, a military training centre in Ukraine aimed at passing on his, and other veterans', frontline experience.
He told Forces News it seems as though the Wagner Group is recruiting a lot of guys who in civilian life are "football hooligans".
"A lot of extremist, right-wing guys," he said.
He added that these new Wagner recruits do not necessarily have "much military experience and very little competence".