Its not an offensive at this stage, its been a probing action with very few troops committed to the attack.
Supposed to be a lot held in reserve but who knows, I think they are just happy to grind Ukraine and further deplete them.
Russians are quite happy to use glide bombs, missiles and artillery to do the business. It was notable that glide bombs are now hitting Kharkiv which means they have pushed the front back far enough that Kharkiv is now within range of these bombs. If you believe it, they will soon be able to bring artillery to bear on Kharkiv also.
