Is it possible Prigozhin wants the caverns? That's a lot of lives to spend on salt (which BTW, was not used to pay Roman Legion troops, more a matter of it being an issue for a Centurion if his men didn't have it available at mealtime). It's not clear to me that they're of great military value once the surface is taken - and I've pointed out before the US found a 'solution' to clearing large tunnel systems during the WWII Pacific campaign - a matter of using combustion to deplete oxygen. Given the size of the caverns that might take quite a lot of combustible material.
