We already spoke a while back about the underground complex of tunnels below Odessa in southern Ukraine, and how they seem to head towards underneath Turkey.
Bakhmut has well over 100 miles of mining tunnels. I think that the Ukraine is a key exit point for underground influence.
"... this [Bakhmut] has a unique landscape, ravines and heights, which are natural tunnels. And the icing on the cake is the system of Soledar and Bakhmut mines, actually a network of underground cities. In which there is not only a cluster of people at a depth of 80-100 meters, but also tanks and infantry fighting vehicles move. And stockpiles of weapons have been stored since the First World War “
Read the article at this link: https://sonar21.com/what-is-ukraine-hiding-in-the-bakhmut-salt-mines/