More about the Russian Wagner Group in this thread http://freerepublic.com/focus/f-news/3632066/posts?page=81#81
But it is not a private military group as that is illegal in Russia. This implies that the suggestion
https://www.obozrevatel.com/russia/rossijskie-naemniki-prikryivayut-dolzhnostnogo-prestupnika-putina-po-vsemu-miru.htm that the Wagner Group is part of the Russian state is correct.
Here is an article in English by Warsaw Institute think tank - https://warsawinstitute.org/putins-invisible-army/
Poles are watching Russia very carefully.