I am gathering additional infos on the matter; if I am able to, tomorrow or the day after tomorrow I will give an update.

That said, if you are referring to the 42nd Mechanized Brigade, it’s just elements of it and they should have arrived in Kharkiv Oblast during the last month - they left Chasiv Yar after they were relieved by the 67th Mechanized Brigade around mid-March. A few subunits of the “Kraken” Special Detachment should have always remained in Kharkiv.

TDF units absolutely fight in the hottest sectors, usually by being attached to the mechanized etc. brigades, and incidentally they are the ones who often hold the positions in the zero line (even the worst ones), are involved in small arms battles etc.

Anyway, at the moment the Ukrainian forces that are fighting in that area either were already there or otherwise in the vicinity. There has been no transfer of forces from other areas yet as far as I know, and after all, there would not even have been the time for that. I will write about this in more detail, but the units currently involved on the Ukrainian side are detachments of Border Guards, elements of the TDF (brigades and separate battalions), and individual battalions of brigades of the Ground Forces that were in the area for R&R while the rest of their brigades are fighting elsewhere. On the Russian side, battalions of the 11th Corps and companies of the new 44th Corps are involved. At the moment I don’t think the Russians enjoy a large numerical superiority.