As part of its broader counter-offensive, Ukraine has gained impetus in its assaults around Bakhmut in Donetsk Oblast.
In a multi-brigade operation, Ukrainian forces have made progress on both the northern and southern flanks of the town.
There has been little evidence that Russia maintains any significant ground forces operational level reserves which could be used to reinforce against the multiple threats it is now facing in widely separated sectors, from Bakhmut to the eastern bank of the Dnipro River, over 200km away.
Yeah, that part is a huge deal. Reserves are how you prevent and stop breakthroughs. Without them, you are in an incredibly vulnerable position and must insure the lines hold everywhere.