the supply must come into battlefield , its not important where is battlefield or your troops are local or not , do you think Ukraine troops are from Lohansk ?
It actually, because supply depends on geographical location, say your frontline is bakhmut, Russia cannot ring supply in from Popasna, or Sieverodoetsk you have to go back as far as at least Luhansk if not all the way back to Rostov. Which mean long supply line and more importantly PREDICTABLE supply line, which mean it is prone to attack. Because there are only a few road you can go from Luhansk to Bakhmut (actually only 1, P-66 Highway), All Ukrainian need to do is to position their long range artillery within range to intercept those road, couple with US intelligence who monitor where those column come from (US most likelyy have 24/7 intel on road traffic into and out of Russian control territories. And Ukraine can intercept those column.
On the other hand, in Ukrainian term, defending Bakhmut, they can draw supply from literally anywhere. It can either be from the North in Slovanisk or from the West in Pokrovsk, or even further, you cannot predict where that come from, which mean it is a lot harder to interdict.
its also the case about Ukraine if Russia manage to disrupt behind the lines , Ukrainian face the same problem Russia have right now .
The key word is "IF" that is why Russia stop making progress since HIMARS get into play, and that is why HIMARS is important. That's because the present of HIMARS push Russian out of effective artillery range on those target. Because if they position within 20-30km (max range of Russian artillery) they now will either be noticed by Ukrainian drone and attacked or COUNTBAT by Ukrainian rocket artillery station further away when you fire your artillery.
If you go back on the footage, before HIMARS introduced to Ukrainian battlefield, there are sporadic report on Russian attacking Ukrainian arms depot and storage facilities (remember the missile attack on a mall where Russia say they were used to store weapon and munition?) When is the last published footage of Russian strike on those target you saw? More or less the strike footage you saw is Russian launching drone and attack energy structure these day.
so there is no different at all , Ukraine supply line come from west of Ukraine to the east of Ukraine , Russia supply line come from west of Russia to east of Ukraine .
I am not talking about weapon or munition, I am talking about Food, Water and Fuel, Ukrainian don't need the west to supply them food, water and fuel (err,, may be fuel, I don't know) Russian Troop in Kherson retreated not because they ran out of ammunition or manpower, they retreated because essential cannot be brough forward into Kherson because both Antonovsky Bridge and Kerch Bridge was damaged. They cannot sustain the winter if they stay put there, that's why they withdrew.
On the other hand, the length of supply line only come into play if your supply chain is interrupted, because it takes times to fix that line because it is longer, but it wouldn't matter much if they can remain uninterrupted, because you will keep on your supply schedule everyday, not matter if you start 300km away or 3000 km away.
its not like usa meddling in middle east that had a 12000km long supply line . for both country the supply line is several hundred kilometer at most
Actually, it did, at least at the invasion phase, which is what Russia still are at the moment, at the invasion phase, everything US military use come from either the US to Kuwait to the front, or Germnay to Kuwait to the front. I personal know this because the fact that I was being used as infantry officer instead of a cav officer (which is my MOS at that point) is due to supply issue, my Bradley wasn't in Iraq when I was in Iraq.
Post invasion phase, the government of Iraq support the US, then everything can be produced or found locally, again, Russia is NOT at that phase yet.