Artaxerxes
Look out, he's got a gnu!
A military thing that's a political thing...
You'll have heard by now that only between 30-50% of the Russian force on Ukraine's borders have actually crossed them - well, it's now pretty clear that it's not just a numbers thing, it's a capabilities thing: Vlad has not used his most capable Armoured units, he's using his 'B' units - decent stuff, but not the stuff with the latest upgrades, the best exercises, the Officers with the best reports.
The obvious question is why, and perhaps we should look to Vlad himself - he rambles on about the NATO threat, and perhaps he actually believes it? Perhaps he's keeping his most capable units in Belarus because he fears that while his B units are dealing with the Ukrainians, NATO is going to roll across from Poland?
He's making his problems worse: by using his B, and eventually C units, and them being less effective than his A units might, he's giving the Ukr time, and each day, as Russian units stagnate or advance, the Ukrainians get more effective, and his units less as the Ukr gets better at hitting the logistics tail and cutting - it's an unholy vortex, the longer it goes on, the worse it gets, but he may be unable to do the thing that might work, sending his most capable formations in, because his deranged paranoia is tell him that he needs them to keep NATO out.
(A units are regular units that are the best equipped, best trained, best lead, B units are regular units with old(er) equipment, less well trained, less well lead, and C units are reservist and conscript units that are equipped with obsolete gear, get very little training, half their stuff will break down and they'll have no protective gear like jammers, reactive armour, and their Comms gear will probably be crap. Last on the list for fuel, food and ammunition).
Source?